I would recommend that you call and talk to Axiom personally. They have no problem talking to you, and their phones are open late (like 11pm eastern!). Tell them about your room, and your concerns with the VP150. Oftentimes problems like the ones people talked about are due to room acoustics. With the two powerful tweeters on the VP150, it is very easy to get overly bright without some absorbtion and level adjusting. Of course, speakers are also a matter of personal taste, so some people might just not like the sound of the Axiom speakers.
Before you buy though, talk to Axiom at 1-866-244-8796. Also, go out and audition some other speakers.
Axiom takes off 5% when you order like 5 things from them at once. There is always the possibility that you won't be satisfied with the system, so you might want to just get the M60s at first (and maybe the VP150) to see how you like them and save on shipping costs (if you have to return them). Axiom might just be cool enough to give the discount even if you order in two batches, though I can't make any guarantee on this, it's just speculation.
Lastly, check and see if there are any Axiom owners in your area. There is a list
here. You'll have to join the
message boards to PM one of them, but it shouldn't be an issue. The list is of owners who are willing to have prospective owners come over and listen to their system before they decide to order.
Edit: Review of the Epic 80 system (different towers and sub than my recc) by
Audioholics. You should PM ClintDeBoer and ask him what he thought about the VP150.
Edit2: It's best to have "timbre matched" speakers, that is speakers that tend to sound the same. This is especially important for the front three speakers, so no, I don't think you should go for a different center speaker than the VP150 if you go for the Axiom M60s.