I got a Brasilia RR45 a few years back as my first grinder and recently received £700 which is around $750, at least for today.

I was thinking about using this money to upgrade the grinder. It would suffice for something like the df64 with SSP burrs which was my first idea. I was wondering if anyone had both and could say if there would be an appreciable improvement in grind quality.

I can spend more (say $1000) if that seems like a more reasonable step up. I also don't mind looking for used grinders or those that need modding, including things like working on mains circuits or adding microcontrollers, but probably only primitive metalworking/3d printing.