A couple things.
1) Yes, the case it too small.
2) Things you're missing that can be key components to a well rounded modular setup: Clocking with mult/div, utilities to control signal strength and polairty, a proper mixer with aux send/return for your effects (and thereby a proper output module, whether it be the audio mixer itself as here, or a separate module), good robust effects (a multi-FX 3HP spin chip module isn't going to get you super exciting results effects-wise) -- the effects here can be nabbed on the secondhand market for below average prices currently (mostly). A Versio is a bit pricier but it allows you access to all the 7+ firmwares in the line, giving you an effects powerhouse, so long as you have a PC and a micro USB cable to change them out when you wish. The change out process is very easy.
My advice: Double the size of your case, get a proper mixer like a D.O. Mixx by Blood Cells Audio or at least a Cosmix by Cosmotronoic, get a couple decent effects, get a Pam's New Workout or some base control for BPM and clock divisions/multiplications, get a proper audio VCA like a Tallin. Also, ditch all the Behringer crap bc it's a garbage company and you'll be stuck with their worthless toys with no resale potential. Here's what I'd probably try to put together in your shoes, with a mind to keep the cost somewhat under control.
