given what you have, you may have good luck making your own exhaust, and adding in a used aftermarket silencer... my exhaust is stock from the header pipe to the back of the silencer, then i put an FMF powercore2 silencer on... it noticably woke up the engine, and it keeps it quiet enough to not piss off the family....too much...LOL
my write up...which i never really got all the pics for...
http://chinariders.net/showthread.php?t=12698