My piece of advice, don't try to spend less on cheap power supplies. Meanwell PSUs suck. Go uZeus or 4ms Row Power, some modules are picky/demanding when it comes to power, others pick up the buzz from the PSUs. Same with bus boards. Shrouded ones are the best, flying ones, less so.
Also, if you plan to go cheap, maybe you should think about semi-modular synths first. I mean, with the amount of money you'd spend to get a decent modular synth you could buy a Polivoks fitted for midi in perfect condition...