We recommend a Makita RT0700 (some folks have managed to forgo a BitRunner and use a Makita RT0702).
We do have an 80mm spindle mount and matching spindle in development, but no idea of its power requirements.
I actually use a 220V (European household) spindle on my machine w/ a step-up transformer:
(though I didn’t get the nifty variable speed setting — I use a BitRunner for on/off)
which has been working well, though as noted in that thread it required an adapter plate.
That said, I wouldn’t characterize it as “best” — it was a pricey indulgence, and the only reason I could justify it was that I had been doing so many test cuts it felt as if I was spending more time wrenching than the machine was cutting. I also don’t push the unit hard (some folks have reported chatter in cuts in the quick-change variants), and I’m still trying to sort out dust collection — currently using a flat adapter plate which works, but lacks adjustability. Debating on hacking up my Sweepy Pro and then working out how it could be adapted…