If you want to put the pc on a shelf with other home theater components, then you might want to consider a rack mount chassis. Here's the one I am looking at:http://www.circuitspecialists.com/prod.itml/icOid/2073
NOTE - This is a very plain chassis and it's a little less than 14 inches deep. The aluminum front panel is blank. That would mean cutting for external drive bays, fans, and switches. This is more for case modders.
Norco has some nice rack mount chassis in a variety of sizes:http://www.newegg.com/Product/Product.aspx?Item=N82E16811219029