Yep - it all comes down to power supply...
an 85W amp with a serious high current power supply, is pretty likely to do better than a 120W amp which runs out of puff in its power supply.
Unfortunately it is very very difficult to tell where the specific amp is at, and where it sits in relation to the X3700 - and especially given the possible combinations and permutations!!
What you have in the X3700 is a very capable set of amps, but a power supply, that in an ideal world, would power only 2 channels.
So how do you parcel out your available power supply capacity is what it comes down to.
The "hungriest" bit in terms of current is usually the bass - but it also requires power - so do you allocate the X3700 to drive the Woofers in Biamp mode, and the parasound to drive the top end? It's one of many possible combos!
I experimented with BiAmping - combining my Onkyo TX-SR876 and later my Integra DTR 70.4, with a pair of Quad 606 power amps... Simply replacing the internal amps with the Quads achieved a slightly smoother - better midrange - the difference was however very slight (and possibly not discernible in double blind testing) - running the Quads in Biamp might have improved things marginally - another step that was potentially an improvement but probably not enough to tell in double blind. - I also tried the AVR's on their own BiAmping... no benefit gained there.
The Quad's are 140W@8ohm the AVR's are also 140W@8ohm...
After reading various articles, and reading that the speakers designer used to demo them with 500W@8ohm Class D amps.... I came across the Crown XLS2500 ... 440W@8ohm, 1200W@2 ohm - roughly in the same category as what Anthony Gallo used at demo's.
Got a pair used, so it didn't cost too much - and sure enough - that was a noticeable improvement. - I tried using them BiAmped ... not a noticeable improvement - tried them bridged too - again no audible improvement.
I hate to say it, but the results are not easily predictable - too many variables - in my case the clue as to what might be optimal, for my speakers, was what the speakers designer had used to demo them with at audio shows - and finding an amp similar in spec achieved great results.
I purchased those amps as an experiment - and I was willing to give them up if it failed, and resell them again - instead they have stayed with me the last 10 years.
To some degree, you really have to try them out.
If you have audiophile friends with spare amps lying around - try those out too.
Amps and Speaker matching can be tricky - in my case, I feel like the issue got resolved with massive overkill.... I could probably achieve the same result with less than half the 8 ohm power.... as long as the amp was also capable of at least 400W @ 2 ohm... the key being high current into low impedance load (for my particular speakers) - but such amps are not all that common - and tend to be much more expensive than what I paid for my Crowns.
In my opinion, an amps capabilities into difficult loads is a critical factor - can it drive a 2 ohm load continuously, at the appropriate power/voltage levels for your listening requirements.... - This won't be an important factor if your speakers are "pure" 8 ohm - but if they have crossovers that drop the impedance way down (not uncommon) - then in the real world the ability to put out major amounts of current become critical - and a heck of a lot of manufacturers don't provide any 2 ohm specs.... making it very hard to tell whether a specific amp will handle it or not.
The Quad 606's I have - were specified as "unconditionally stable into any load" - and the manual shows a chart of the available power at various impedances - sadly... although it has heaps of power at 8 ohm (140W) and 4 ohm (165W - already showing current limts), at 2 ohm it is down to 90W... which in voltage equivalence is the equivalent of 22W into 8 ohm.... - giving a clear idea of what the limitations are - the AVR's were probably showing exactly the same symptom. - An "Ideal" amp should double down as the impedance halves... so a 150W amp at 8ohm, should become 300W at 4ohm and 600W at 2 ohm.... sadly almost no amp achieves this... true high current designs will multiply by around 1.7x into 4 ohm and a further 1.5x into 2 ohm.
I did the experiment and am happy with the result ... for now... at some point if the opportunity arises, I may seek out a more audiophile alternative to the pro/pa Crowns - but so far they have bettered some fairly serious competition.
Don't hesitate to experiment!
Would be running 2.1 setup (Pair of Genelec G3 + sub). Thanks!
