All of the PCIe x16 2.0 cards are back compatible with 1.0 slots and all 1.0 cards are forward compatible with 2.0 slots with very very rare exceptions.
The 8800 GT's not a problem.
That's a reasonable deal but as Fulmer said, the EVGA cards have a lifetime warrantee and a 30 day upgrade (pay only the difference) program.
That's also a factory overclocked card. You could take the standard card and overclock it yourself and save a litte but with you'de probably void the warrantee where the factory OC'd card would have the full warrantee. Something to consider.