BFG 6800 GT OC bottlenecking my system?

I don't have the fastest rig any more, as my mobo is older, last of the AGP boards(DFI LanPart UT NF3 Ultra-D). You can see the rest of my system in the specs. Here's my problem i just got my 3800X2 to keep my sytem decent for the next year and half until i sell the whole box and start anew. I oced it to 2.5ghz and it ran stable in games for at least an hour(no it didn't crash or anything, i just didn't play any longer). That was my initial stability test. Then I benchie in CSS performance test on all default which is all high with HDR enabled, 1280x1024, 2xaa, 4xaniso. I get 101 fps stock on fw 81.98's and the 8.22(V5) forceware remix chipset drivers with SP2. All cpu and vid clock speeds are stock, then i oced to 2.5 ghz and ran it again, 102.73 fps......102.73 fps? I then proceeded to check with CPU Z to verify it was acutally running at 2.5 ghz and that ram to cpu was 1:1 and HT is on 4x so the HT is not oced at all. This is very strange, i got no performance increase for a 500 mhz cpu oc on a dual core processor, which is acutally sort of like a 1ghz oc(2 cores). Yah the games are optamized for dc yet, but it still makes a little difference. Anyway, does it seem like the BFG 6800 GT OC is the bottle necking factore here? I thought the GT's were still pretty decent cards, i got it the day i came out, about year and half ago. Its not that old and was close to best card out at the time. What else could be causing that? I have to have fast writes disabled because of the 6800/NF3 stuttering glitch, but everything else is set normal.