Tough Budget.
I think that the Axiom M22ti mains would perform better than polks, but would the Axiom QS8s or in-wall speakers be an option? You can also get creative with brackets like some of the omnimounts that connect to the ceiling and would thread into the Axioms.
After purchasing that receiver for about $350, you only have $650 left for speakers and a sub. The Axiom M22s would cost $400 from the outlet and you could save for a good sub, center, and eventually surrounds.
If you want all 5.0 channels for $650, check out the Bic Venturi and Athena Audition series lines. I think these are more feasable in your budget. A cadence X-Sub for <$300 might be a good option, or save for one from SVS or HSU.