Daedalus, when it comes to the warranty if you purchased a base model from BestBuy than the warranty is only a year, but if you purchased from Newegg or other online resellers generally you get 2 years directly from Asus.
As for the Processors you go from the following
720qm - 840qm
6mb cache - 8mb cache
1.6ghz - 1.86ghz -- Base Speed / Core
2.8ghz - 3.2ghz -- Turbo Speed / Core
$364 - $568 -- Current prices listed by Intel -- Probably MUCH cheaper from an OEM or online reseller if you know where to look.
But any true gamer knows any bit of performance increase helps give you an edge over your competition, and where it comes to the professional side of thing, when you can shave Seconds/minutes/hours off of a render or encode when upgrading easily replaceable items it's well worth it from a productivity standpoint.