Do bare in mind, when receiver makers rate their units output you need to look carefully at just how its been rated.
I know of no rec which is going to outperform a likewise dedicated outboard amp, and thats where Id suggest you look to get more power, IF thats all you want.
Onkyo rates theirs into six ohms driving only 2 ch. Integra is the higher water mark than Onkyo, yet usually supports lower outputs in terms of watts.
If youre looking for functionality as well as a step up in power, normally the top two levels of nearly any receiver line is where to look. There are some which purport 200wpc, like Sherborne. Many of these power house recs also are pretty costly as they will give more bells and whistles in the bargain. Sometimes for as much as $3K - $4K new.
Id say add an outboard amp personally, but the notes above are correct on where the vol knob rests in your rig. I set my own rec to an upper limit of 75% before buying external amplification. Ive no idea where my vol is set to and its upper limit is still at that same 75%, which may or may not be effective now with external amps in place.
To prove my point, the last external amp I bought is rated at 150w @ 8, all ch driven. 10wpc more than my Onkyo, and the resultant sound is both more available, and better sounding. I choose to run it in 3 ch mode and up the ante on the power to about 200 wpc @ 8, and in 2ch its over 200 wpc into 8. Its far better across the board than was the Onkyos amps!