That might be a problem if it wasn't for
Intel SpeedStep and
AMD PowerNow!. These technologies, built into basically all laptop chips nowdays allow for on-the-fly processor speed control. Essentially, when you are say, running on batteries and doing word-processing, it can run the processor at a much lower speed, taking lots less power. When you are plugged into the wall and running a game however, you have the full power available.
Also, consider that AMD or Intel chips, from the lowest to the highest models, are pretty close in physical size - the only difference is the amount of cooling needed.
Really, if you are planning to use your laptop for anything other than mobile school use(in which case, get an EEEpc), you want as much power as possible. Sacrifice some battery life if you have to; Its cheaper to buy yourself a car-charger or one of those 150-W plug-in car inverters to power your laptop(which I would recommend no matter how much battery life you have, if you use it in the car a lot).
edit:
Ooh! Just looked on Newegg.
Perfect. Laptop.2GHZ X 4, 6GB of ram... 1GB video ram... N.I.C.E.
A little pricy, but you should never have trouble with it. Its also made by HP, and seems to be good.
Get it either at Newegg or cheaper at
Buy.com-Robbie