1996 Toyota 4Runner Performance intake and exhaust

I installed a K&N air intake system about a year ago and noticed an immediate increase in power and acceleration. As well as a little better gas mileage. It really helps me enjoy the ride up the mountain to ski.

Will installing a performance exhaust system give me any additional increase in performance? How much? If yes, which one(s) will have the mildest sound? My wife doesn't want to be embarrassed when we drive through our neigberhood, and I don't want to raise the attention of law enforcement as I drive by.

Thanks very much!