one other factor to look into is portability...which takes into account the size of the screen, battery life and laptop weight, and other add ons like external harddrive, as important factors...no point getting something so heavy you don't want to bring it around...
4GB RAM...you gotta be kidding...cause 4GB of laptop RAM (2 pieces of 2GB) is gonna take up most of the budget...you end up with like $500 to purchase the laptop ;p
firewire 800? might as well have eSATA...much faster and lower processor overhead...
ultimately, Apple is not necessarily better...don't believe the propaganda...people who use Windows and Mac intensively for work can tell you neither has any real advantage...believe it or not, under work stress, both will crash as willingly...and the parts that go into a Mac are just like those in a Win system...fitting your budget and requirments, and not brand attractiveness, should be your priority...