I am putting together a monster of a 64bit machine with a couple of pci-e x16 cards (I want to have 4 monitors). I was wondering if anyone out there has a system like that on 64 bit. Mostly I am worried that there won't be drivers available for any random card that I choose for 64bit Vista. I want to keep the price to a couple hundred dollars per card or less. Any suggestions?

As for "random card", there's basically only NV and ATI out there. The driver situation is about the same for both, and not that different between 32- and 64-bit Vista.

Both ATi and nVIDIA have pretty good support for multiple monitors on any of their dual head video cards. Im running two monitors right now on this system off an old 9700 (my 9800 started doing weird things after 7 months of dual monitor). Havent tried dual on my 7800gtx, but just looking at the two I like the ati control center for configuring this kind of thing. As for Vista, I cant speak about it, as I use XP64, but it seems the sound card situation is petty fudged on vista right now from what ive read. Beta drivers everywhere, and some semi old games (hitman blood money) are simply broken sound wise on vista, so you might want to investigate the audio situation as its currently whats stopping me from doing vista.

Thanks!