Hardcase, that'll optimize your connection for dowload speed, NOT for gaming performance, particularly first person shooters, but AH/WB3 still somewhat apply.
MTU can stay at 1500, but having the TCP receive window cranked up uber high is detrimental to you shooting people, and has a positive effect for your opponents regarding the shots you receive FROM them. TCP 1323 should absolutely NOT use windows scaling, and the receive window funtions best with cable/dsl with a setting of 32768.
I can get 3.5 megabits from my cable on that test site if I tweak it for max download speed, but when I've got my gaming tweaks enabled I'm around 1 megabit or so, which is optimal for gaming with the local cable around here.