http://www.xbitlabs.com/video/mx400/
Check out the site rsiep: alot of information and comparison between the mx, mx-400 and gts. Alot of benchmarks to check out as well.
I believe that if you want to buy a video card and are not planning on buying another one for a long time while also ensuring good playability for future games, buy a Geforce2 GTS. Like I said in one of my previous post: it will take you where no mx can..