yes, I think it's an eSATA port.
An Athlon 5000+ is less than $100, I suggest 4000+ which only costs $60, since the 780G board supports hardware decoding, a cheapest dual core cpu is good enough. You should be able to overclock it to 2.6Ghz-2.8Ghz easily.
For intel platform, E2160/MCP7A...