I've made this PC to be Vista ready, and it has run all the pre-release versions of Vista without a hitch and with all the visual effects enabled. The motherboard also has built-in Dolby Digital output so it would make a great HTPC along with the TV tuner. Also, the X-Fi sound card sounds VERY good especially if you hook it up to a 5.1 computer speaker system.
The video card is about 6 months old, the motherboard and processor are about a year old. I put it together myself, and it runs flawlessly. It's been a great computer and should suit you well.
Looking to get $500 for it as it's still pretty powerful and quick.