Bit late to the thread, but yea Raspbery Pi will make for a good Media Center type of PC.  Which is what I Plan to use it for.

I've been playing with Pentium 3 and Pentium 4's for render farms you can look up my posts here.

And 6 older computers couldnt keep up with a single Core i7 Processor... I dont know if that comes down to inefficient network rendering in Bryce or a Core i7 is that good.

My latest test will be using a AMD Quad Core Processor + 3 or 4  Core 2 Duo PC's as nodes and see how that renders.