I'm running the 4" Rineharts, and they have a nice deep sound; no high-pitch whine at all. I had originally wanted the Monster Ovals, but my mechanic told me the Rineharts perform better at low RPMs. He also says that the 4" are different than the 3.5"s. Very happy with them so far.
I'm running V&H tru duals and Rinehart 4". I like them way better than V&H slipons because of what I call a hammering sound that V&H seems to produce.
This setup is nice at cruise and is loud when you twist the throttle. Much much much better than the 3 1/2" Rineharts.
For grins I put back on by stock 2-1-2 decattted header. More muffled sounding and has more of a muscle car growl than the tru duals. They were quieter as well.
For me, I like the tru dual sound better.
Sure if I was building a monster race motor I would have a 2-1 but my motor is stock except for adding GMR 577 cams.