Re: nVidia Riva TNT2 pro and Compiz?
Compiz runs pretty well with my Geforce4 420 Go which came with my notebook (celebrating five years this september and it has only 32MB of dedicated graphics memory!) As Thunderbird said you should be able to get some really cheap, relatively old graphics card and still be capable of running compiz.
GA-MA790GP-DS4H, ATI Radeon HD3300, AMD Phenom X4 9850, 4GB PC8500 [Ubuntu 8.10]
Toshiba 2450-201, GeForce4 420 Go 32MB, Pentium4 2.4GHz, 512 MB PC2700 [Ubuntu 8.10]