NVIDIA SLI (GeForce 6800 / 6600 PCI-E): i7525 platform -
It's perfectly clear that the SLI technology is effective. It even provides excellent performance gains where system resources do not lay severe limits. All this happens even despite that one PCI-Express slot operates as x16, and the second - only x4 (there are almost no other options, only x8+x8 is theoretically possible). But there is also a fly in the ointment so far. During our tests we sometimes witnessed artifacts (ripples), which, by the way, obviously demonstrate half-frame operations (between GPUs). There occurred color distortions sometimes. That is NVIDIA still has some issues to fix in the drivers.
Chaintech GeForce 6600 GT AGP -
This card is also very overclockable to give you more than you paid for which is always great. All of the necessary accessories are included to take advantage of everything this card offers and the software bundle is great. If you are looking to upgrade your video card but cant afford a 6800 and don't want to make the jump to PCI-Express this may be exactly what you are looking for.