So - now I got my GTX580 (and all the other stuff accept the Obsidian 650D chassis which will arrive in "two weeks"! Doh!).
Never the less - now I could do the interesting test of throwing in a GTX580 in my old rig to try how CPU limited it is - and YES it sure is
My old setup and score:
Core2Duo E8400@3.3 - GTX275 - 6 GB DDR2 800Mhz - P45Mb
-------------------------------------------------------
Frames, Time (ms), Min, Max, Avg
6851, 218058, 9, 69, 31.418
-------------------------------------------------------
My new setup and score (just swapped the GTX275 for a GTX580 which should be a LOT faster):
Core2Duo E8400@3.3 -
GTX580 - 6 GB DDR2 800Mhz - P45Mb
-------------------------------------------------------
Frames, Time (ms), Min, Max, Avg
7230, 217293, 13, 70, 33.273
-------------------------------------------------------
So I gained ~1.9 fps in average
Updated my original post too...