Good question, I've heard the long "poo poo" pipes do ok, but I wouldn't know from personal experience as I wanted a performance gain as well. With that in mind I got the SBP tuned pipe and extended the glasspack to quiet it down (four rivets, chunk of conduit, screen tube, and fiberglass insulation is all), which actually worked quite well in combination with the length of heater hose on the very end (they also sell an additional tip muffler as an accessory... but I don't have it);


Skeptics Review of SBP Tuned Pipe

If yer not too concerned with it's lack of visual appeal, this modification helps baffle the intake scream quite a bit;
Remote Airbox (& intake silencing) on the cheap

Here's a few vids on the subject - bear in mind that my cam doesn't really do justice to the subject and this was before I did the glasspack extension;
http://motorbicycling.com/f15/sound-...ber-12466.html

These mods combined result in the clutch whine becoming very apparent, so you might wanna attend to that as well. There's been a ton of suggestions regarding that - I've found a coupla coats of rubberized undercoating on the inside of the clutch cover does a pretty good job.