Hi jonesy.
Your component selection is very similar to the system i already own. So, from my own experience, i can say your expected equipment will be well matched.
I recently bought the Onkyo DS797 to power my M60s, QS8s, VP150 and EP350 subwoofer. The Onkyo brand name is well known for a'v receiver quality and the 797 came highly recommended to me by an audiophile professional friend. Onkyo is by no means the only solid brand name out there but it is a good choice.
It is capable of 6.1 channels and can power 4 ohm speakers such as the M80s.
If you are interested in different features or would like to hear some different receivers then i highly recommend you head around town and do some auditioning in local stores. You dont' have to buy, just go and listen.
In regards to your subwoofer question, that is always a personal decision. Just offhand though, the M80s are known for putting out a good range of base so i would suggest you try out the M80s first and if you want more bass or a dedicated sub then simply pick one up later.
As for choosing Axiom over Paradigm or Klipsch, the easiest way to answer your question would be "price for performance ratio". The Axioms are alot cheaper for equal or better quality than many of its competitors. Ultimately though your own ears will have to decide what is best for you.
good luck
