The recommended PSU for GTX570 is 550W you have 500W This might suggest that it is under powered. You should see significantly more horse power with 570. It compares to 260 in SLI.
So Perhaps upgrade your PSU to at least 850W just in case you will do SLI in the future.
You're right but I'll be able to compare shortly with a similar system I had, my old board and video card, the only difference will be the dual core E6600 and 4 GB RAM instead of the E6320 and 3 GB I had before.
I'll post here as soon as I can.
Meanwhile I'll try my new PSU and see if it makes any difference with 3DMark11.