Geforce8500 and slimline desktop?

Question

I added a PCI-E low profile Video card (with Goforce 8400 and 256MB) to my HP S3100n desktop system. This card supports H.264 HD video. FULLHD videos still lag, but they lag less compared to connecting the onboard video port.
Will the video get better if i change to a card with 8500chip(still 256MB)?
Can the reason be refered to the power is only 160W?

Answer 1

that could be an issue.
but the 8400 is a bum card. see if you can get a 8600 at lease or an ati.