AMD acquired ATI several months ago and at this point the branding change is complete. ATI == AMD (look at www.ati.com
and find out for yourself).
Secondly, the notion that you "need" a discreet graphics card for "usable" performance is absurd. Sure, I certainly wouldn't want to run any extremely graphically intense games on an integrated chipset, but for the needs of the poster, it seems to be sufficient. The X3100 now has a full shader core and pretty reasonable performance for a composited desktop and perhaps some casual gaming off to the side. If the X3100 is fully capable of running the beheamoth that is Windows Vista, I'm more than certain it can take on compiz, especially given my past experience with compositing on intel chipsets.