If price is not a limit then I strongly suggest that you get a new PC. The PCI bus runs at 66Mhz and has a maximum tranfer limit of 133MegaBytes per second.
That can't come close the the AGP's 266Mhz 1.1GBps(that is for AGP 4x, 8x is theoretically twice that).
The PCI bus' speed is the total of everything you have in all your PCI card slots. So, if you also have a sound card and ethernet card, you won't even reach 133MBps.
The "best" PCI GFX card, which is really a waste of money, is the GeForce4 MX, which is just a glorified GeForce2. I don't follow useless products, but that's probably under $100.
I strongly recommend, that if price is really not an issue, that you get a new system. If your worried about losing all your data, a good company or shop could put your old harddrive in your new system.
If you know what your doing you could build your own high-end system for under $1,000.
[Edit:] Right, u wanted a link:
Linky