Those're expensive synths, yep. Too bad they weren't expensive before you opted to uncase them and stick them in a 6U Rackbrute.
Nope, not kidding. Let's do some math...
An Arturia 6U Rackbrute = $359. It has 171 usable spaces in it (176 minus the P/S), so 359 / 171 = 2.10 per hp.
Moog Subharmonicon = $699. It occupies 60 hp. 2.10 x 60 = $126.60. This makes the Subby's actual cost $825.
B. Neutron = $299. It occupies 80 hp. 2.10 x 80 = $168. The final cost of the Neutron then becomes $467.
This idea might seem convenient, but as in the rest of reality, convenience has a price. If you keep these two synths in their own cabs, with their own power, you wind up saving just short of $300. And there's another factor to consider: what will it cost if you screw something up in the uncasing and recasing of those synths? You might be able to get Moog to fix the Subby if it gets damaged, but the Neutron? Nah...Uli built those to go in the trash if you blow 'em up.
Frankly, Jim's plan above makes a lot of sense: populate the cab with modules that expand on not just the 2S, but all of these synths together. By not cramming 140 hp of a 171 hp cab with just two patchables, you then have space in which to build a pretty beefy expander system for modulation, timing, extra VCFs and VCAs, etc. But as the build stands at present, you've got a whole 31 hp for actual modules. That should raise red flags immediately...because while the Neutron and Subby already have power and cases, the Eurorack modules you'll want to add do not.