In the $600 price range, it is generally agreed that the SVS and HSU (and the Outlaw LFM-1) give you a bigger bang for buck over the Axiom EP-350. The EP500 and EP600 are in another price bracket (and out of my budget).

The Axioms will give you matching speakers and I am sure most people will be happy with their performance.

Since I won't demo all the subs, it'll be either the SVS PB12-ISD or the HSU STF-3. I honestly don't think I can go wrong. If you put a gun to my head now, it's the SVS by a nose.