Upgrading system for HD Playback

[mayamaniac]

Currently, I have a small form factor PC. It's an intel P4 2.4ghz with a Geforce 5500 128M. I'm using it as a SageTV Client connected to an HDTV via DVI. Its working fine playing SD content. When playing HD, of course it stutters in VMR9 mode, but in overlay its mostly smooth, stutters once a while.

I would like to make a few upgrades to make it play HD smoothly in VMR9 mode. Now the problem is this PC doesn't have an AGP slot. It has built in intel graphics and a PCI slot, which is currently occupied by the GF 5500. I checked a few sites and the best PCI card I can find is this BFG NVIDIA GeForce 6200 OC 256M. Is this the best PCI card available? I can also upgrade the CPU to something faster. I think the motherboard should support at least up to a P4 3Ghz. Now the question is whether these two upgrades coupled with PureVideo will be enough to get smooth HD playback in VMR9 mode?