Wanting to build HTPC PVR Server for XBMC setups

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I'm looking for ideas on how I can build a small pc, with dual hdmi tuner cards, that I can use to import (as well as outputs to control) my HD Bell Satalite.

Than wanting to tie the two streams into something my Multiple XBMC Gotham machines can access, where the XBMC machines remotes can control the satalites channel, view guide etc.

I am using the Pivox XS systems running linux and XBMC Gotham on my tv's.
So would need an independent server.
Would be interested in the ability to pvr within the server, possibly ave recorded shows for later viewing in the xbmc?

so questions:
What's the best card? HDMI in, and do the cards come with IR blaster outputs to controlt he box, or would I need to buy these (x2-4)
Best software for this, I'd prefer a windows install as they always seem to work easier, but linux is okay also.
What sort of machine spec's needed for this? dual HD, recording pvr etc.

Thank you!