You could also buy the 350 if you decide before the 30days you want to upgrade just call axiom and pay the difference between the 2 subs. i have the same setup as your looking at with the 350 and im happy. but the 500 was not available when i purchased mine or else i would have gone that route just because i was ready to spend money. now i might upgrade the sub but its not at the top of my list.
Jake

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Leave the gun, Take the canolis.