congrats on ur purchase.. hope u enjoy it. and congrats also for upgrading the warranty..
3 laptops? WOW! one for urself, one for brother and one more for who?

although it is class 3 but still ok lar.. its just like 8400 mah..
if u want to think bout 9500 and 8600 then sure need higher budget.
class 3 still can do a lot of gaming. dota sure can.. of coz COD4 and Crysis will big problem lar...

to ur question.. higher digit does not mean better...
high end 8 series is much much better than low end 9 series.
so like 8600 and 8800 are much better than 9100 and 9300..
9500 is almost like 8600...

ur laptop slow already?? so fast?? how much ram is in it?? how much available memory left (check in task manager under performance)...
ya.. antivirus eat resources... hmm... i dont get why can be slow... try to define slow... like what happen and what u were using..