I just put on a universal slip-on muffler from Roadkrome. It was $68 on ebay, so you can't beat the price. It was a little to quiet with the original baffle in it, and it was too hollow sounding with the baffle completely removed. So what I did was make a custom baffle from some 2.5"I.D. car exhaust pipe. I just cut and bent out some slots and wrapped it in fiberglass. It sounds great and I can definitely feel an increase in power.
http://www.yamahastarstryker.com/index.php?action=gallery;sa=view;id=1232
http://www.yamahastarstryker.com/index.php?action=gallery;sa=view;id=1232