I had the PB12-nsd, it was a very capable sub, I found it a touch punchy for my liking. the FR graph shows a bump in the response from ~50hz to 60hz by about 5 db. I think it was this bump that annoyed me at times with music. I did manage to get it to smooth out with a little better placement in my room, but opted for the PB13 Ultra, it has a flat FR like Axiom's subs. I think if the EP800 was available at the time I would have gone with that.

I think in your price range, most of the subs do not have a flat FR so this should be a non-issue.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70