The Muse was a slot loaded 6th order design - not doubt current modeling software could come up with a simpler - perhaps sealed? solution.
Whatever enclosure design you settle on, I'd suggest at the bare minimum to partition off a sealed section for the woofer. Ask a repair tech at a hi-fi shop about long term reliability of built-in amps on commercial subs - even name brands like B&W, Paradigm, etc.
6th order vented involves building a 2 order high pass
into the feedback loop of the subwoofer amplifier.
Its not complicated if you know what you are doing.
(The inverting input can be treated as a unity
gain point for standard unity gain filter design).
Typically 6th order is a vented box tuned much lower
than normal, with a peaking high pass coincident with
the vent tuning frequency to bring up that region.
Many alignments are possible, hard to say which is best,
but IMO maximally flat is not a good idea at all, IMO its
best to aim at a slow roll-off of say 3dB/octave* and let
the relatively predictable room gain do its work.
* Down to the vent tuning frequency. IMO a high pass
with Q of about 2 (+6dB peak gain) is about right.
Using Jeff Bagby's sub woofer modeling program I came up with both woofers wired in parallel, in a common cabinet of 140L, using 2-3" x 10" ports tuning the enclosure to 24Hz. I'll be using a PE BASH 300 amp. I am somewhat concerned that the net impedance will be about 3 ohms or so.