I've built DIY speakers and I feel you can get more for your money up to a point. I don't know what that point is, but a speaker manufacturer can do more advanced testing, tweak the design, try different drivers, etc. It also depends on what you do for a cabinet & finishing. Solid hardwood with a nice finish can be expensive as well as time consuming. My standard-cheap solution is to wrap the speaker in leather-look viny (like a guitar amp/speaker). Brown "blends-in" with wood furniture, but used white once, with black grill cloth.
If you don't mind a larger cabinet that can be a DIY advantage. Manufactures often compromise and make a more compact cabinet which is cheaper to built, ship, and stock, and many customers want smaller speakers, especially for multichannel setups. A larger cabinet isn't always better, but it's one constraint that you can eliminate.
I would NOT buy from Aliexpress, eBay, or unknown 3rd party Amazon suppliers, etc. Try to find drivers from reputable manufactures where you can go to their manufacture's website for specifications. It's really the
manufacturer that's important. Parts Express, MadiSound, and maybe Simply Speakers are good places to start.
For the mid-woofer get the
Theile-Small Parameters and then use speaker design software (such as
WinISD) to optimize cabinet design and predict performance.