heh this is the massive problem with control systems - not quite there. The crestron will simply replace the remote control - not much else. You could use RTI or similar and do much the same task, including the matrix switching...
Now to push my own barrow (but I'm not pushing, lets just be clear

) but have a look at
www.digitalhomeware.com for an alternate solution. Network based control and EPG solution...
Oh and by the way, the new linksys mce extenders are a _really_ good option for extra zones, mini-itx as suggested before are still noisy (in general) and have much the same problems of larger form factors. Plus, its really hard to compete on price - $300 is such a bargain. Oh, and they're embedded.
The ultimate solution really is a big fat central recorder and very thin network clients, then puff goes the matrix!! And your control solution comprises a simple IR remote at each endpoint. So so long as you don't intend to mix other sources in, you'd be sweet. If you do, cheaper to do it at the endpoints.
DHW make a 1ru mce machine, based on a mini-itx too, but again, heat (and therefore noise)! Hush are great too, but hellishly expensive.
Anyway just my 2 cents.
Arne