The best PCI card out right now is the v5 5500...hands down. I think maybe the only thing that could come close would be the kyro2 pci, but it has yet to surface. I tried the geforce2 mx pci and returned it b/c it can't touch the V5 in terms of speed or visual quality. Also, the PCI is only a frame or two behind the AGP, which is even more impressive for a PCI card. Getting one cheap is becoming harder and harder. I got mine around 2 mos ago on Ebay for ~$105 with shipping, but I think the price is going up, particularly on the PCI version. Most vendors don't carry them anymore, your best bet is on Ebay through resellers or picking up a used one or off of the forums at Voodoosource.net. I've seen a few there willing to part with their V5's for around $80 bucks, but that is pretty rare.
Chiz
PS oh yeah, if you feel kind of adventurous you can get the PCI Mac version and flash the bios to the PC version....totally compatible but you may run into some problems if you are unfamiliar with bios flashing. The Mac can be had for about ~$20 less.