My audio brothers and sisters, my audio spirit is striving for a new project, a reference level, "I listen to it every day", kind of project. The problem is, I'm not that great at crossovers and all that math stuff. I can build any enclosure you can show me, and cost isn't a big problem (well, let's stay in the under $1000 range for a DIY project). What can I build that is high efficiency and, hopefully reaches a new level of audio high.
My taste in music is jazz, classical, chamber, vintage rock. I'd prefer small to large designs and don't mind adding a sub if needed. My room is larger, probably 16 x 20 x 8. My audio trek has already taken me to Fostex land, where I've been happy, but wished for better low-mid weight and less "paper" sound. My quest has also taken me to a nice slice of pi called the Thermionic 3pi, but the WAF wasn't great, and I'd like more precise imaging. My quest has also run into open baffles of various sizes shapes and configurations. Right now, believe it or not, I'm listening to the guts of a Dynaco A-25 (improved tweeter and crossover) mounted in an OB, with a sub filling in below 150hz (but not high eff). This is to say, there is no particular design I'm partial to or hold sacred, but I generally feel that simple is better. And I like triodes, and low power amps and I love dynamics, so high eff is the way to go.
Recently I've found myself aimlessly buying drivers on ebay, and have four Electro Voice vintage 12", high Qt drivers coming my way (Sp12b), and I've ordered some Arurm 2Gsi tweeters, but frankly, don't have a good idea what to do with all of them. The single driver site seemed to suggest BR, but the box would be very big.
Okay, ramble is over. What should I build? I've got on hand FE167's, FE166's, FF85k's, a couple of vintage Utah 12's (high eff, low Qt, but cab needed), I have coming the speakers above (EV's and tweeters). I've got guts for 4 Dynaco A-25's... but I'm willing to buy what I need.
What ideas can I get from the collective wisdom of this group? Again, if a crossover is needed, I'll need help. I'm okay in the woodworking department. What should I do?

Single Driver speakers don't sound good on most music.

So; have you thought about a compound driver like the P-audio series?
Smaller box and pin-point imaging.

You can get much better sound by choosing good used speakers than by building your own for the same money if good sound is what you are after.