I would upgrade your sub first.
If your room is largish, and his is smallish, and you have bookshelves and he has floorstanders, I think you might more likely be "underspeakered" more than underpowered. If his system "felt" more powerful, I would be looking for a bigger/more powerful sub.
Ask yourself this: If you had a sub like the 500, would your system feel more powerful? Not only would you be reaching much deeper than your 175, but the additional power of the 500 handling all the bass would free up your receiver's reserves quite a bit.
I think you would have to have a HUGE jump in amplification to "feel" your M22s more.... and I think even then the results would only be slight in comparison to the dramatic difference of a bigger sub.
