Air Filter

Ok, I know this may sound stupid but i popped off my tank today and cracked open my airbox to take a second look at my Air filter.... And, Oh My GOD! it's horrible, it's even smells like old meatballs. I'm Going to replace it, but i was wondering was kind of power gain i might receive by going with a K&N Hi-Flow Filter. The bike has 22k miles on it atm, and it still runs like a scolded ass dog with this filthy Breathe rag. I just wanted to know if it's worth spending the extra 45 Bucks for the K$N Hi-Flow. Anyone have xperience with these filters? I figure the gain should be pretty sufficient, but just want some pre-Insight. And i've also heard of the Air-Box Mod (cutting 2 1-inch diameter holes on each side of the airbox and popping in circle screen filter fittings.)...Anyone done this and had any good things to come from it?