The lack of PCIe 2.0 support shouldn't bottleneck a v1.1 card. I think that you probably have either a driver issue, or just have the settings up too high in-game for the card. Crysis is the most demanding title out - if you can play that with no issues, then the card should be fine. However, you should check your settings and make sure they are actually manageable for your card. Certain levels of AA and such can really take a hit on any card's performance.
Also, if you provide information on the actual model of motherboard, rated timings and voltages on your memory, those pieces of information are pertinent to their resale, though the $200 guess is probably about the most you can expect to get, from the sound of it.