I don't trust Gateway ...

For me, after HP, Dell, Toshiba, Lenovo, Asus ( in some case ), you fall in a lower-end range than these brand I mentionned.

The hard-drive is too slow. Try to look for a 5400 RPM.

In a 15.4", the ATi Mobility Radeon is the best GPU you can find I think. However, if you find a X1600 of a Go7600 from nVIDIA, this could be better to have more fun and better graphics.

You won't have the same gaming performances than a desktop. A laptop is made to work, not for gaming ( my opinion ). Having a powerful GPU is for graphics applications like Adobe products and Windows Vista Aero Interface.