Advice on Sub for HT and musical accuracy (with a twist)

I am planning a custom sub for my home theater but also want a accurate sub for music. I plan to power my sub with a Hafler XL-280 amplifier but this could change as I am also looking at a couple other options. Regardless power output will be in the 250-300 watt range.

Now the twist, I am planning to utilize two new in box, old school M&M Electronics Godfather 15s as the drivers for the sub. Partly for nostalgia reasons, mostly because I like the way they sound. Always have.
Anyway, I have the T/S parameters for the subs and I am planning to build a rather large enclosure of around 6 total cubic feet of internal volume and then mounting the subs in a push/pull configuration (NOT Isobaric).

So this is my plan. I would like to hear thoughts on this configuration as I have never before used a push/pull config but I have heard good things about them. (Actually, I have never BUILT one, I did one an MK Designs MX-200 years ago) I am planning to leave the enclosure sealed, the M&M subs have a low EBP and to go vented the enclosure would probably need to be in the range of 15cuft for both subs. a bit larger than I am prepared to go.

Any advice appreciated but please don't tell me things like go buy new subs. I already have a Paradigm PS1000 this is a "Fun" project for me, I just want to make the most of the endevor.

Thanks in advance!