My first module was the Mother 32 and I now have a few others built around it in a small Doepfer (LC6) case. Personally, I did it this way because the M32 packs a lot of features into a single module at a really good price. If you worked out what it would cost to get the same functionality from separate modules, it would be a lot more. The one thing I don't use very often on the M32 is the sequencer, it's too slow to work with. If you like the Moog sound (it does sound Very good), I say start with the M32 and build up around it.
I've actually started to think I might take it out of the case and put it back in its original enclosure, it's really fun to have right in front of you to play and it works very well standalone. Something very 'pure' about it :)