pinky4life - Its best to have the two cards at the same specs if you can, if you buy 1xAGP 256mb Nvidia Turbocache card, and 1X PCI-E 256mb turbocache, this will improve system performace, as the turbocache takes work from the CPU, so two of these, is 512Mb, and the two cards can share resources, but not as well as SLI. But no, performance improves if you have two identicially speced cards...sorry bout speling
Fiercepc - My mobo with an AGP and PCI-E slot, well both the slots can be used at the same time for a wannabe effect of SLI, you do not need a physical bridge, they share resources between a little chip between the two slots, they can be used at the same time for multiple montors, dual monitors whatever you want... comes in handy having two cards, I can game on the better one, while surfing on the other, I plan to buy a PCI video card, so I can have three TFT's running at the same time, one for games (PCI-e) one for surfing, or watching movies (AGP), and one for music and email checking (PCI) - or I MIGHT buy`a few of those USB to VGA, and have evan more monitors
Sorry to of chatted on, but I hope I explained it ok