The specs seem fine. I have an Inspiron 1501 with AMD athlon64 x2 1.7 ghz, 2 gb ram, and ati radeon xpress 1150 graphics and I get about 35 fps. I think your system will get more than 50 fps.
If you have any spare cash I really suggest you don't get the 4-cell battery, it'll only give you about 1 hour. The 6-cell gives you about 2 hours, and the 9-cell gives you about 4 hours (that's the one I have and it's awsome).