The large RTi series require a LOT of power to sound their best if you have a big space or like to listen >-10db often.
If you like how they sound but do not seem to be dynamic/punchy/loud etc... as you would like, an amp upgrade might be worth a look. If you're OK with all that then a change of speaker might be what you are looking for.
The PSB speakers are more efficient but are 6 ohms (at best) and will be a little tougher on your AVR.
And it would be best to buy from some place that has a good return or trial policy/period. Not everyone likes the same sound. Or better yet demo the speakers you're interested in.
Klipsch RF-62II, RC-500, RS-400, SVS PC12+,
Def Tech SC8000
Harman Kardon AVR 1600
PS3, Apple TV, Sharp 70" Qattron