The interface you need, hands down, is an Expert Sleepers ES-8. Eight DC-coupled outputs and four inputs with a USB or Lightpipe interface to the computer. And with this, not only can audio go in and out, but by using ES's Silent Way software (or, on a Mac, also MOTU's Volta) you can also send and receive CV/gate/trigger signals via the same interface to control the modular or, via the inputs, have the computer 'track' the modular's behavior.
As for the Moog 104hp skiff, you'll have to be very careful with your depths. A better choice...as well as a potential source for a bigger cab...might be one of Erica's powered ones. Module depths make more sense, plus you have ample power via their OEM supply, which frees up space on the patch panel, and they're rather cost-effective. Stackable, too, via interchangeable end-panels.
Module-wise, this isn't a bad start, but consider something which can mangle incoming audio under CV control. Have a look at MakeNoise's Morphagene and/or Phonogene...great choices for external processing.