I am thinking of the same thing, the drivers I am looking at are:
1. 871S - Tangband, $17 each, 3in dia.
2. 1337 - Tg., about $55 each, 4in dia, 87 db, Titanium based
3. 1320 bamboo- Tg., about $45 each, 4 in dia, 90db, Paper based
Note the model nos. are incomplete, just do a search.
the last 2 models, some users gave very good reports about them, dynamic, clarity, etc. If eff. is not a worry try 1337. The disadv., lack of power handling capability.
Logitech uses 871S on their model 5500, 5.1 system. 871 is good and cheap.
Use them in dipole config., ie 2 driver per side you will have a very good system, and most important easy to build and cheap too. The conf. will beat any commercial system in the market.
If you have a commercial computer subwoofer, then it will complete your system setup, cheap and excellent sonic performance.
hope this helps.