MOTM

I would take the depth of the MOTM modules such as the 300 and add 
at least 2 inches.  If you build one of the Blacet/Stooge panel 
modules such as the Time Machine you will need the extra depth.  
Additionally, you never know what you're going to want to do in the 
future.  When I built my cabinet I put in slanted rows similar to 
the Synth of Doom.  I've found that I can only mount certain deep 
modules like the Blacet conversions in the lower rows, which are 
deeper.

By the way, as a big fan of 2001, although not a big fan of Nietche, 
I love the monolith/Zarathustra concept.