IIRC, Dayton lists FR as 30-140, but no mention of if that is -3 or -10 dB at 30Hz. Even the Sub1500 doesn't reach infrasonic output.Maybe or maybe not based on the OP's "Seems like I can either get punchy back with no lows or all lows and no punch."
So if he can get enough "punch" already at some positions it might be possible to level it out without losing too much "punch". It's definitely worth a try with position/EQ first before throwing $$$ of subs at the problem.
I haven't found a CEA2010 report on any of these subs. I know BB likes the Sub1200 as Best Budget performer, but not much out there beyond that.
I am not fully recommending that OP goes and spends money they may not have, rather identifying an issue related to his primary concern. There is only so much that Cabin Gain can do to help out a Sub like that, and it is a distinct possibility that their room treatment could be hampering their goals.
We need to be honest about that. For everybody that extols the necessity of acoustic treatments, far too many are applied with little-to-no understanding of acoustics or guidance from a person who does.