Cambridge CXR 120 with Polk Rtia7 in stereo mode performance ?

I am posting for the first time here. I have a couple of questions that I was hoping the experienced folks here may be able to help me with.

I bought myself a pair of Polk Rtia7 A7 speakers that were on sale for my stereo setup to replace much older Polk R50s which were really entry level. These are powered by an older Onkyo TX8522 @100wpc. I've had these speakers for a couple of months now and with every passing day they sound nicer. Initially, they sounded bright. My research seems to indicate that these Rti A7s are power hungry and could sing with nicer amps.

I may have found a Cambridge Audio CXR 120 at a nice price point. This is a 7.2 system but delivers 100wpc in stereo mode and 60wpc all channels driven. While not higher in power than the Onkyo, I see that people say purer power makes a big difference. So, my questions are:

A. From your experience friends, will the CXR get me better sound than my Onkyo with the Rti A7s if I run it in stereo mode? Typically, we listen to music and care about music sounding good. We watch lots of movies as well but are happy and content with a two channel setup for watching movies.

B. The receiver is spec'd at 60wpc all channels driven. How do amps pump more power in stereo vs when using more channels? How is the circuitry driven?

I appreciate the help friends!