CV, I think you are on the right track with the receiver. I gave a Yamaha AVR (HTR 5640 I think) and some surround speakers to some friends who had a circa 1995 $1200 Sony rack stereo system. We were all amazed at how good the Sony speakers sounded when we switched out the receiver. You may even want to try your Polk speakers with a new receiver. You may be impressed. As a Polk and Axiom owner I should echo what the other have said about the speakers. Polk makes some very good speakers so depending on which model you have the difference between Polk and Axiom may not be that impressive.
Also, I know there a lot of people who favor separates, but with my modest $300 HK AVR 230 I can crank it up to where I like it (meaning it doesn't really sound "loud", per se, just "appropriate for rock and roll" but not straining or distorted in any way) and at that volume I can't hear my pager on my hip or my cell phone in my shirt pocket or the house telephone 6 feet away (or my wife arriving home and yelling at me to turn it down). Based on that I have decided that I don't need separates. Going forward, you may decide that you need them and you may want to get that started now, but don't underestimate the AVRs - particularly the brands recommended by the Axiom gang.