A bunch of us were just talking about this in another thread. There are reports of guys that can find that magic combination of timing, placement, phase, and slope that allow them to integrate different port tunes and configurations. There are many more (myself included) who banged their head against that wall and didn't find a satisfactory solution. I would definitely stick with configurations and port tunes that are as close as possible for ease of integration.
The GSG suggestion is a fantastic one. If you look on their "classified" section there's a guy from CT looking to split an order (would save you on shipping costs). I've built a half dozen of their subs and they're a very enjoyable and simple build.
SPEAKERS: 3 x DIYSG 1099's LCR; DIYSG HTM 6's and 8's surround; 4 x RSL C34E's atmos.
SUBS: 4 x UM18-22 Mini Marty's and 2 x 21DS114-4 Devastators
SIGNAL CHAIN: Denon X4400; Minidsp 2x4 HD; 2 x Jensen Iso Sub 2RX; 3 x NX6000d.