I'm in a similar search - I have retired my old Dell Dimension 8200 (2.4 P4 cpu, 2 GB RAM, 160 & 250 GB drives, ATI 550 Pro tuner card) to PVR duty. It is working pretty well with BeyondTV 4.0 and an old Radeon 9550 card and a clean XP Pro install.
My question is: for $100 - $150, what AGP card would provide really noticeable performance increases over my old 9550 card? Or would the $ even really produce a difference I could see? I am recording at high-quality with MPEG 2, generally things look pretty decent, my input is just analog cable (comcast). I'm currently feeding an old but sweet Sony 27" via the s-video line.
Thanks!