Hi Squallaz,
I don't want to take away your enthusiasm here however if your budget is US$ 850 (let's say Euro 800), perhaps you shouldn't start with an Eurorack system. A "basic" Eurosystem (depending on what you want) starts in my opinion with at least several thousands of dollars/Euros. Below US$ 2000 I think it's difficult to get you something that you need. With US$ 3000 it's getting better but you still want and need more ;-) It can go as high as US$ 5000 or more and than you still want & need more, that's the "lousy" part of Eurorack, the initial start up of getting started with Eurorack is immense expensive.
Why you don't look for a (semi-modular) desktop synthesizer (like the Grandmother you mentioned) and start with that first? If you still enthusiastic about that then perhaps in the future you can consider moving to/adding a Eurorack system?
If I would be you, I would spend US$ 850 into some nice desktop stuff, and start saving money for a Eurorack system, then let's say, if you are still enthiousiastic after one or two years and then consider a larger budget.
Naturally, that's totally up to you :-)
Kind regards,
Garfield Modular.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads