I have an 8300 mgpu which runs alright but I need a lot more for HD video-playback and I plan to buy a gt 240 but I wonder if SLI between the 2 gpus mentioned above (SLI) would perform better than gt 240 alone, since it doesn't have SLI. If you guys are wondering why I chose 8400 gs it's because my budget isn't that high so I chose it. I have like $120, very poor. I'm considering about buying 8600 gt too but nvidia recommended 8400 gs so I'm not really sure. I'm a noob at building PC. My step-dad built this PC for me but I just found out that this PC just can't satisfy my need for speed.