Guys, take note - not Ultra-90, XP90... yeah, that old archaic one.
But anyway... you would definitely see a big difference. I would guess the U120extreme would get somewhere around 37-38 idle and 45 load (depending on the fan, of course, and depending on if it needs lapping or if it is lapped).
Before you spend the money, though, you should probably know your temps aren't too bad as long as full load hits under 60. The Ultra 120 extreme would definitely cool down your system and give you more headroom, but if you're short on cash, you don't necessarily need to make the upgrade.