IMO get the cheapest GF8300/8400/8500 you can get your hands on.
I think this would be perfect, complete with HDCP support should he later want to use it for a home theatre computer to play protected BluRay or HD-DVD disks;
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150241
The Gf8 series gives him all the benefits of nVidia's improve 2D quality compared to their previous GF7 generation, and all the nice little bells and whistles for video decoding, large panels (dual-link TMDS), etc.
It's 256MB dedicated memory with the TurboCache option for more incase it becomes an issue (unlikely for what he's doing).