But I didn't really explain/answer anything I just posted the related data.
I did play Xenoblade on my E8500@4.05GHz and GTX285 with no issues at all.
Used 4xIR (the GTX285 has 512 bit ram and 160Gb/s!)
I used a build with HLE hack, because normal build had some audio issues.
I did use EU version which is 25FPS, so that might be why I had no issues at all running full speed.
Most E8600 should do 3.8-4.0+ GHz with a good cooler.
