First off this is what I'd pick:
Axiom; 2-M22ti, 2-QS8, and Hsu VTF-3
Since you're 80% HT...the QS8's are amazing surround speakers.
Now on to your questions:
1) Those specific ones...no. But I did listen to NHT and Polk before deciding on my Axioms. The Axioms have TIGHT bass, a superb clarity. Nothing touches their clarity.
2) see #1
3) ?
4) ?
5) I believe there is more to it, because both axiom and Hsu are ported, and their bass it TIGHT.
6) Most people like speakers with good immersion ability as the surrounds (QS8's are better at this than any surround I've ever heard. I switched from Polk LS f/x surrounds to the QS8's. There's no comparison) For the rear one or two channels most people tend to opt for a direct radiating speaker. (I personally have the M2i's in the rear.)
7) I haven't heard the Polk center
8) ?
9) see #7
10) Needed? No. You may
want the extra oomph of a nice Rotel receiver, but most any receiver will drive any of these speakers. (I have Rotel myself and love it.)
11) I don't know why it couldn't
12) Depends on what you mean by "future proof". If I were you, I'd get the best 5.1 receiver you can get. With the QS8 surrounds you won't miss those rear channels.
13) Visit
Club Rotel for all your Rotel questions. They can help you best.
14) see #13
