I love my TORs and catbypass. Loud but not overly so, at least for me.
It is not worth getting only the TOR pipes. They need to be coupled with the catbypass to get the performance and noise benefits.
I've heard the Staintunes and honestly don't like the sound as much as the full TORs. Not only were they quieter but the TORs give a nice roar at throttle that the Staintunes don't match, at least for me.
It's not quite true the TORs plus bypass are not giving you most of the power. They are but need to be coupled with a correct tune to take advantage. I'd also recommend the 20055 tune over the 20054 as it does give more upper end power, but still isn't really that dramatic a change from the 54. See this thread for details on tune power restrictions...
For a dramatic power boost. Get a Tuneboy and remove ALL restrictions.