i have the two bros bf slip on for the 250r...it is ridiculously loud and piercing.
it really bothered my ears when i didn't wear ear plugs, and even when i did wear ear plugs.
just going from 10-50 it sounds like you're revving your bike to the limit.
idle is also very loud and obnoxious, i genuinely felt sorry for pple that had to hear it.
i was getting ready to sell it...then...i came across a two bros p1x power tip :
http://www.gixxer.com/forums/showthread.php?t=238610
you mentioned the p1/p1r power tip. i've been reading that it generally doesn't offer a noticable diff. only 1-2db lower, but the p1x is very noticeable, but it might even be "too quiet" at times.
it has completely changed it. it isn't high pitched and piercing to the ear now, it has a more modest lower growl. idle has changed to the point where it isn't waking up the neighbours in the morning, and when you're not pushing it, it sounds like it now. but when u do, it still has a loud rumble that i love.
it'll be quiet when u want it to, and loud when u want it to.
it came with the bike, so it saved me alot of cash
if i got to pick out of all the slipons i've heard, it would be the akrapovic (if u want it loud-ish) or the areaP (quiet core).
just my two cents, and my experiences with the two bros can.
btw i love it now though haha.