I had a 600 in my HT. Swapped it out for 2 EP500's. I prefer the two 500's. I have since replaced the V2's with V4's, and they are an improvement over the V2's by a large degree. The sealed subs are crisper, and less boomy.

I would like to try an 800, but my room just won't fit one. The 2, smaller subs just work better in my room.

And I hate to add this, but will anyway. I've had 6 Axiom subs over the years. Every single one of them required an amp replacement. One needed a driver too. But, they've worked without issue, for at least five years min now, after the amps were replaced.