Considering the MacBook Pro starts @ $1199.00 and the alienware @ $799.00, you could ebay the mac, eat about $200.00 and get a base model 11x... However, you'll be disappointed when you learn the base model 11x won't touch the speeds of a MacBook Pro, and you'll be stuck with a $799.00 mini-laptop that really needs about another $500.00 worth of options to perform worth a darn.
The MacBook Pro has a core 2 Duo while the 11x has a far inferior CPU. However, if you just like pretty lights, on an overpriced, glorified netbook, then go for it. You'll be very disappointed when you get it and the pretty alienware backlights have become mundane.
EDIT: two years down the road, not only will the mac hold up better, but it's resale value will far exceed that of the Alienware. Just wait a year and that 11x can be bought on ebay for about $500.00 for a upper class model.