Similar thing for me but Im at a 3.4ghz quad, 8 gigs of ram, 5770 x2, running at 1920x1080. Tried very high and high, lots of problems, then tried normal. Works "fine" but my system should be able to handle this game on very high.
This game is pretty badly optimized but a small advice would be if you turn off any other application(like intertnet browsers) then it would greatly improve your performance. Also if you're playing on DX11, turning off advance DOF would greatly improve your performance too.
Right now I get a average of 30-40 frames per second with res of 1400x900, settings on very high, on DX11(with testalation and advance DOF turned off), AAA anti-aliasing, Testure filtering AF4X. My frame rate suffers however when ever there are high beams of light particles coming from the outdoors or vehicles. My system specs are:
im able to play it on dx10 high settings at 1920x1080 with AA maxxed and texures maxxed but i dont like the frames per second that i get so i decided to just play it on dx9 everything else the same and it still looks nice and runs nice around 70 fps i believe. btw i finished it today and i loved it. for this game i recommend using fraps just to test out the fps while ur trying to find the right video settings for ur rig. helped me alot. i messed with it for like an hour trying to see which settings i like best before i finally decided what setting i wanted and then commenced playing. loved this game i cant believe i let it fly under my radar. i will definitely be buying metro 2034 and the planned 3d sterescopic version of 2033... cant wait!
i have a i7, gtx260 9 DDR3 if you wanna know my specs.