IMO, if it ain't broke...
However, if you really want to tamper with your perfectly usable system, I suggest getting something like Norton Ghost and backup your current config. Then you can download a trial of Theatertek, which uses the Nvidia decoders. You probably will get a nice improvement in picture quality even with the Radeon 7200 video cards. Then if you still aren't satisfied, an upgrade to a Geforce 6600 may help.
However, if you really want to tamper with your perfectly usable system, I suggest getting something like Norton Ghost and backup your current config. Then you can download a trial of Theatertek, which uses the Nvidia decoders. You probably will get a nice improvement in picture quality even with the Radeon 7200 video cards. Then if you still aren't satisfied, an upgrade to a Geforce 6600 may help.