Polk RTi10 vs. Paradigm Studio 20 or Mini Monitor

Try the monitor 40's - just a little bigger than the smaller ones and almost as good response-wise as a full range.

Ultimately, I would suggest speakers which:
a) sound best to you
b) fit your budget
c) are aesthetically pleasing to you (and the significant other!)

Now my personal opinion: I am assuming you are developing a home theater environment from your mention of a center channel speaker. If that is the case, the Studio 20s would be a good choice coupled with the obviously forthcoming subwoofer. This combination will allow greater placement flexibility (independent placement of your low frequency source) than a floorstander. As a bonus, I can imagine this combination would perform well for 2 channel listening too.

While the Polks may provide enough bass extension to perform satisfactorily in a 2 channel system, they likely wouldn't supply the same 'WOW' factor that a dedicated subwoofer will.

If you have to get mini monitors look @ used Merlin TSM's they are great.

First, "in the corner" is not necessarily the best place for any speaker. Pull them away from the walls, to the extent tolerated by She Who Must Be Obeyed.

The corner is often exactly the right place for the subwoofer, which you are getting to complement the monitors, right?

Hey,
Since you like all 3 choices, How about letting the wife go along on a listening and decor audition,all 3 can be a good match for the yamaha, but a sub and quality stands would be needed for the monitors.