Don't let Lugia hear this, but the Behringer stuff isn't bad for simply for the oscillator sections.
The Boog aka Model D has a stack of three oscillators + noise, 1v octave CV, with a Eurorack level oscillator mix output (pre-filter) and doesn't require racking... for $300. Plus, it's a full MiniMoog clone all on its own. I don't think you're going to find that kind of functionality for $300 if you source everything individually. Granted the oscillators aren't capable of hard-sync nor have individual outputs. But if you go with the 0-Coast and you want some analog to go with it, it's an option.
The Neutron can be thought as a utility box that includes sample & hold, slew generator, a couple of extra ADSRs, attenuators, two VCAs, filter, etc. Plus two oscillators that can hard-sync.
I wouldn't call either ideal for replacing dedicated, individual modules. But they are worthy of consideration if you're trying to get more out of your set-up with limited funds. I've used both as stand-alone synths connected to my DAW for a few tracks... because sometimes you just want something quick without a ton of patching.