HTPC for high-end system and Linux plugins

I'm looking into a HTPC for custom install, usual dual core, graphics etc which I have a fare idea. However it needs to communicate with Creston system, over IP, play CD's, DVD's, HD-DVD's, Blue Ray. And also to rip/encode the previous without any user intervention (flac, retrieve CDDB, replaygain, etc) and also for video, either original size or recompressed (high quality) Ideally Linux. Video going to be sent into HDMI switcher and then onto HDMI 1080P projector. Audio isn't important for now, just using SPDIF until sort out that side. Must have Sky HD and freeview tuners. ATX size.