It seems to me typically when someone asks this kind of question he/she will end up getting an amp regardless of what we say here. As he said he would like to have the power and not need it, so he has to get that amp for sure.
Having said that, Polk Audio recommended 20 to 275W for the Monitor 70 so I think adding an amp will allow him to listen to higher SPL, more than enough to damage his hearing, but obviously he won't do that to himself. He may also perceive better sound quality, mainly just perceive, like most people who is all set to add an amp would, I guess.
It took me years to realize I get much more sound quality improvements by listening only to high quality recordings, after getting a couple of pairs of high quality neutral sounding speakers. Now I can enjoy high quality sound whether I use my old Denon AVR, or my 3 separate systems. If I had realized that sooner, I would not have 3 separate systems, probably still have one though.