I so hear you, and have been looking for a single box solution for the past year. But a bit of history--I first heard the all digital tri-amped Meridian speakers in Atlanta--maybe 1994, and having the concept explained,
I thought damn, this is so elegant and patently superior, it has to be the future of audio. Notion tucked aside until about 2003 when I read about the DEQX--maybe Stereophile? Curious enough that I talked to the nice folk down under and found a demo for 2/3'rds the asking price of gulp 3800. Wasn't quite sure exactly what I was going to do with it, but thought OK this is going to be the future of audio, and I don't want to be left behind. I'm tired of spending small fortunes for speakers that leave me yearning for even more expensive upgrades of questionable value--here's something to at least
get the impulse response close to correct, and maybe, just maybe get off of the upgrade death spiral.
It was a weird happenstance that I happened to have some unassuming JBL bookshelf speakers (300/pr) I had just bought for the bedroom along with a pair of expensive ($5K) Infinity speakers I had on loan from a nearby Best Buy back in the day when they had the Magnolia high end stereo/HT departments, also on closeout. By this time in my audio life, I'd been through some nice speakers including Infinity Gamma IRS,
Thiel Cs 3.5's, Dunlavy SC-IV's and Newform Reseach ribbon/Scan Speak hybrids--all in the 3k to 7k price range, and all very fine speakers but all left me wanting for something better--little less edgy, better focus, whatever.
And there was enough of an engineer (hard nosed prove it to me type) left in me that no way I was going down the Krell, Audio Research, etc path. Too many other things to do and other ways to spend $$.
Bear in mind that I had never used the DEQX for anything. It took the better part of a day to get through the manual and get grounded enough to try a project. The baby bookshelves--which sounded pretty good (6.5" two way, the tweeter recessed within an elliptical wave guide)--seemed like a good place to start. Two hours later I had them sounding almost as good as the Infinity's and this w/o bypassing the passive XO's.
To say I was dumbfounded is an understatement. The Infinities were returned the next day. This is not to say that one can make a silk purse from a sow's ear, the dynamics were limited and no way could the tiny woofer keep up with a servoed, 400W dedicated amp 11"er. But it was close enough over a range of material and volumes that it sealed the deal for me.
Now nearly 20 years later, I have designed and put together 4 actively powered and digitally filtered 2 and 3 way systems that are sufficiently satisfying that I rarely even visit audio places.
Yes I was able to break free of the addiction. 3 of the 4 systems were because of one theft, two moves, first to smaller digs and then larger quarters, and one which was good, but just never could get quite right, but still use it for a second desktop system. On the way, I learned a great deal about transducers, their various shortcomings, how to measure them, and even to rout a perfect circle with less than a mm of gap.

And bought countless saws and clamps on the way--need a saw, I now have a jigsaw, backsaw, holesaw, table saw, circ saw, hand and hacksaws, and have made a bunch of sawdust on the way.
What I have discovered is that designing and building a very, very good loudspeaker is not the arcane art of yesteryear. The primary problems are in no particular order: 1) diffraction including baffle step 2) matching sensitivities 3) seamless XO's 4) displacement limits, 5) compensating for driver FR anomalies, and 6) getting a decent power response. All of course should be housed in something non-resonant and pleasing to the eye. The drivers need not be expensive if they are well chosen and mate well with the others. Of course, there is nothing wrong with using the sort of components found in a 10,000/pr speaker: typically these might cost somewhere between 200 and 400 dollars apiece, instead of 50 to 150. So if one is on that kind of quest, a reasonable approximation might be had for roughly 1500 for drivers and another five hundred for cabinets, assuming we aren't too choosy about the finish--i.e. exotic veneers.
The crossover design is the biggest barrier by far. Designing, choosing the components and voicing crossovers are all matters of great expertise, and I tip my hat to those with the time, money, patience and tech savvy to learn the art. I was personally either too lay, too busy or both. But in my experience I have yet to find a passive speaker that outperformed it's digital counterpart. I don't say that they don't exist, just that none of the several kits I have assembled for friends couldn't be implemented actively, sounding as good if not better. As an aside, people point out the cost and complexity of active loudspeakers as they require additional amplifiers, but dismiss the very real cost of coreless inductors (ouch) or the right kind of plastic capacitor. Thanks to baffle simulators and great but affordable measuring equipment and software makes a many month effort doable in a couple of weekends. And amps, buy once, not several times.
Going out on a limb with my trusty hand saw ready, I'd say all but power response and designing/fabricating a wave guide are within easy reach--baffle response is still an approximation using the EXCEL based open source software but all but huge errors can be mostly remedied--or the baffle replaced with a different design (cut and test first before the cabs!) Power response is sometimes hard to discern without having the drivers and making many measurements, but using solid rules of thumb such as not thinking that 15" beast of a woofer will mate well to a 1" tweeter because their FR happens to overlap. And there are always kits (Meniscus, Madisound, for example) that have survived the test of time, and can be sometimes be bought without the XO parts. A very safe way to start with gobs of performance/price.
Wow this was meant to be a post related to finding that single box solution.
What I'd love to see: a streamer, multiple digital inputs w/ volume, enough channels to do an active 3 way + sub(s) with both digital and analog outs (the XO filters should not simply emulate analog filters and be min phase up to 102dB/octave), robust measurement and filter design capabilities so as to "fix" the impulse response at 1 meter, and whether it's ATMOS or Dirac Live, a sound correction suite that can average measurements according to users needs, a 10+ band parametric EQ, and have 4 configurations on demand, along with a bunch of preset EQ's for different volumes, types of recording, etc. The DAC's should be of decent pedigree and the SINAID >110dB. And preferably all of this for under $2000.
Anyone know of such a product? I'd buy it in a heartbeat. Anyhow I'd didn't mean to ramble--only to point out that DIY speaker design is becoming more and more practical with an active approach, and maybe get a few thinking about giving it a go. Changed my life. And never looked back. The only commercial speaker I really have to own some day are the Sanders 10E are some other really exceptional planar.