What's MCE2005? I've seen you mention it several times now.
Yeah, the only thing my single GTX ever really struggled on was Oblivion. I had no ini configs done and had all in-game settings maxed except grass/self shadows, and in thick grassy areas (especially the pink stuff) it would drop as low as 27fps at 1680x1050, 4xAA. In fact.. just tried it out again last night by disabling SLI and it still does it:
I didn't have my GTX overclocked, though. It would gain ~4-5fps if so, probably.
Now, those same places w/ SLI enabled at the same settings:
I also have my frames capped at 60 since I was running vsync. I might've been getting higher than that.