What resolution will you be playing at?
I think Metro 2033 is one of those game that brings a card to it's knees. Based on benchmaks
I've seen, you cannot expect more than maybe 35FPS at 1680x1050 and 25FPS on 1920x1200; expect something in-between for 1080p screens (1920x1080).
Also, as blackhamachi mentioned, PhysX would just be too taxing on a dual-core CPU (pretty much any CPU if you ask me) to be enabled with non-nvidia cards. Batman still looks nice and is fun to play without PhysX BTW