Buy the parts for a good gaming desktop and with the money saved you can buy a cheap laptop with a decent battery life for travelling.
There are many fun games (like BL) that don't require a monster gaming laptop to play, and you will appreciate the extended battery life of having a lightweight laptop.... not a big, bulky, heavy, hot (as in "burn-your-lap-hot"...not "lovey-hot" gaming laptop.
I don't own one myself, but I have heard many positive things about these Eee PC's.