It's mostly between 620-640, it went down to 570 for a second when I smashed the buttons like a retard.
fx6100, gtx550, 4gb, w7 64
It looks promising, my only problem was the controls, I prefer mouse for look around, and shooting of course(maybe you could use the right mouse button to run - unless you want a retro, keyboard only game).
By the way if you load your images at runtime it will be much faster(I mean the big background).