Sed, a higher power amp than what you have now in your receiver wouldn't "smooth out distortion" if you weren't playing your present equipment loud enough to produce audible amplifier distortion, which you apparently aren't doing.
Leaving the receiver at the 8 ohm default setting couldn't damage the speakers and would be extremely unlikely to damage the receiver. Since more clean power is available at the 8 ohm setting(as mentioned above), the speakers are less likely to be damaged by inadequate power reserves leading to clipping. If very loud levels were played for an extended time(which you don't do)the receiver might overheat, but its internal protective circuit would shut it down, and normal operation would return after it cools down(having given a hint to turn it down a bit).
