I have a dedicated cctv pc (Pentium G3020 I think with 6GB RAM and 4TB of HDD). It runs a geovision dvr pci-e card without hardware compression for 6 analogue cameras doing motion detection recording. On top of that it runs pcnvr as well for four hikvision IP cameras. I think I'm pushing its abilities a bit but that gives you an indication of what is needed.
Personally I would keep CCTV and media server separate.
Very nice setup. If you look at the second link I posted couple of posts up I have the Hikvision turbo hd package. Not sure how to define it but from what I gather it's ahd system (not ip) that will give true 720p.
So good substitute if not going down the ip Route?