What kind of specs are needed for steam in home streaming?

I have an old nes case, the internals are sadly useless, so I figure I may as well make it in to a "steambox" for use with steam in home streaming. I'm thinking an mitx mobo and probably mini itx power supply should fit in(or maybe a smaller psu if I can find one). 4GB ram is cheap, and a cheap 60GB ssd should do for a linux install. I don't know what kind of cpu and gpu I would need though, would the AMD a4-6300 dual core 3.7ghz apu be enough?

 

I'm trying to get it done for like $300 or less, don't need anything fancy just something that can stream 1080p for steam. 

 

Steam In-home streaming info

The only info they really state is that:

 The client has more modest requirements, but should have a GPU that supports hardware accelerated H264 decoding. Any recent laptop or PC should meet the client requirements.

Having a browse through this page maybe worth your time.