M11x vs $650 Build

Here's the deal. I was informed that you can get the Alienware M11x for $649 (after $200 student discount). If you didn't know, now you know (my contribution to Tom's) .

Honestly I don't need that kind of hardware. I'm not looking at gaming, but I am interested in computing power and long battery life (M11x = 8hrs) , and really expect the M11x to handle what I throw at it: multiple windows open (literally 100+), streaming video (1080), Excel, Word, mainly applications and not games.

So I wanted to ask you guys. With a budget of $649, what can you build for:
Computing power
Portability 12"
6-8+hrs battery life

Those are really my selling points at the moment. If you can do it for under, great, but if an M11x for $650 is the best deal that I can get or netbook/laptop that I can put together, please let me know.

MTIA,