Thanks John K.
The sub comparison is really just a very subjective opinion given the only constant is a MACC calibration. They are placed differently, in completely differrent rooms, houses, etc. So I have some tinkering to do. I knew I would likely have some issues with the sub given its built in static position so no sub crawl for me. However the ep500 is placed directly under the center and I find it integrates for music wonderfuly - which is the most important to me. Prior the HSU was well integrated for music but still had punch when watching a movie. So far I am missing the punch with the Axiom.
I think I have some old HSU sub tuning cd that I will play around with. However John raise a good point. The integration of the current speakers and sub is excellent and very balanced. I do remember having to run the HSU at about 2/10 on the volume with about -3 db with the MACC in order to get it to balance. The EP500 volume is at 5/10 but an apples/oranges comparison.
Currently the sub is my only "concern" of the system. This has nothing to do with various literature out there about Axiom subs vs. others but just one fairly noob opinion. However I've not concluded anything yet since as more time is needed for tweaking.
In the meantime the more I hear the m80 and vp180 the more I like them.
1 M80,vp180,qs8,aim7,EP500,Denon4520,Rotel RMB-1095