if you wanted only the best, accuton makes a tweeter with the radiant surface made out of diamond. They cost $2800 each and play up to 100,000Hz.
as far as woofers go, accuton also makes a woofer that is very nice. the cone material is made out of corundum and costs about $200 or so each.
if you wanted to simply look at lots of different parts, you can go to www.partsexpress.com and look at their home audio drivers. These home audio drivers usually are very nice and a calibur above car audio drivers. But, their impedances are all weird and you usually won't get max power out of your amp, but if you're into sound quality, so what? = )
DEQ-P9 (30band eq L/R, time alignment, 36dB/oct 4 way crossover)
Soundstream Tarantula (for subs)
Precision Power PCX-4125 (for horns and midbasses)
Image Dynamics CD2 comp mini horns
Scan-Speak 7" 18W/5535A midbasses
Subs still pending.