I’ve got two Doepfer Low cost cases - the LC9 and the LCB, and I’ve never had a problem with them. They are both running the PSU2 (the earlier power supply) as well. I chuck modules into them without a care in the world.
I’ve also got a uZeus and a Mantis; they work fine as well. If you’ve already got a 19’ rack (I’ve one built into my desk) then that’s a decent option.
Agree with the other poster: you will find it hard to avoid buying other modules (I did, clearly) so you might be better off going 84hp first.