Yup, welcome to the club. I have a unit very similar to yours and you are correct on both points. These units ARE noisy and seem to be a little under powered however, the 500 has ample torque in low gear to master most situations. I've heard others say they had to winch themselves up steep inclines that were long. Definition of long???? I have never had to do this but then I don't travel 20 miles up into the mountains. I can't speak to the muffler thing as I have never tried anything of this sort but it does stand to reason that it would cut some of the much needed power from the small 500 cc engine. As for the tire replacement, smaller diameter tires equal lower overall gear ratio therefore increasing the effective power of the engine. There will be a slight deficit in top end but a gain in low end although slight. There is a performance chip available for this engine that costs about $250 that fools the processor into believing the air entering the engine is actually colder than it is, therefore increasing the fuel flow slightly and so the power of the engine. Does it work? I don't know. I haven't been able to find anyone who has used one of them. All of that being said, rather than go through the expense and effort of changing wheels and tires, adding the silencer, and trying to soup up the engine to get more power, trade it for a bigger unit. I'm faced with the same dilemma. Good luck.