Geforce 7950 GX2
Codename: G71, 90 nm technology
2x24 Pixel shaders, 2x8 Vertex shaders, 2x24 Texture units, 2x16 Raster operations processors
256 bit memory bus
500 MHz core, 600 MHz DDR (1200 MHz Effective) Memory
If you have money to burn, the money-is-no-object price segment will offer diminishing returns for the high price tag. But if you have the money and need to play at the highest resolutions available with high levels of AA, then SLI/Crossfire setups are the way to go.
Probably the most reasonably priced and easy to use multi-GPU solution is the Geforce 7950 Gx2, which is actually a single card with two 7900 GPUs built in; it performs faster than any other single card available at ultra-high resolutions.
Keep in mind though that
if you play at 1280x1024 resolution with 4xAA, you would be wasting money on the GX2, as cheaper single cards like the X1900 XTX and 7900 GTX can outperform the card at those settings. But if you play at 1600x1200 with 6xAA, the 7950 GX2 can't be beat by any single card out there.