How big is your room?

The M22s are fantastic speakers. I have a feeling that any replacement tower you choose (e.g. M60, M80) won't make you say WOW as much as it will make you say "Well, it's definitely a bit better."

That being said, I think you'd get more improvement for your money by getting the VP150, QS8s, and possibly a new sub. Your receiver has enough oomph that it should be last in line for an upgrade.