I have decided to take the plunge and purchase from Axiom. M22ti/VP100/QS4 and will be using the DENON 2805. I have decided that I like the HSU 10 inch sub for $525. If I were to upgrade one item what would it be. Should I upgrade the sub to the more eexpensive HSU ($750) after shipping, upgrade my center, or upgrade my surrounds? Any information would be greatly appreciated.