A few things. I would definitely consider this receiver:
http://www.bestbuy.com/site/olspage.jsp?skuId=9245471&type=product&id=1218066769902
It is a Yamaha that supports the latest audio codecs (TrueHD, DTS-HD-MA) has 4 HDMI inputs, and should offer a lot of bang for you buck. I would think that it would meet your needs. It is only 5.1 not 7.1 but if you are planning on 5.1, why pay for more? It sounds like your room is a great size for 5.1. You could also step into the Yamaha 565 if you want more features and power:
http://www.bestbuy.com/site/olspage.jsp?skuId=9245444&type=product&id=1218066766851
Onkyo receivers are also solid values.
The other thing to consider is that if you get bookshelf speakers you will want to get a subwoofer at some point to drive the lower frequency bass. Most bookshelf speakers simply are not built for lower base extension. Not a bad thing, but something to keep in mind if you are piecing together a system. In other words you may want to get your receiver and then get your fronts and then a sub and then your surrounds. Instead of buying a "just okay" 5.1 system I would recommend buying better fronts and a sub since this is where the majority of movies, games, and music is driven from.
Those Polk speakers are pretty good. And I am just like you, I am not a Klipsch/horn tweeter person. But you have other options in your price range. Since you are mostly a home theater person I would recommend reading reviews of the SVS SBS-SCS01 and SBS-SB speakers. They are priced very close to the Axiom's and are highly rated for home theater usage. There are other choices as well such as KEF, Deftech, Emotiva, HSU, and Elemenatal Designs.
Bang for your buck you should definitely check out Elemental Designs. I have one of their subs and their sub and speakers packages are priced very well. Could be a good fit for your tastes and your budget.