Well, after much research and second-guessing, I sold off a few things and bought the Prophet 10 on the latest sale. After playing it for a few days I will say that it's the nicest piece of furniture in my house. It's simply gorgeous. Everything about it feels luxurious. The keys, the knobs, the buttons, everything.
I debated about going for the Prophet 6 (great synth) and if I were a touring musician I would have, but this is going to live in a studio. Plus, I really wanted 61 keys. Had there been a 61-key Prophet 6 it would have been a harder choice.
I've got the single output plugged into a mono-in, stereo-out pedal board where it goes from mono pedals (pitch, phaser, flanger, OD, fuzz) into a Boss Dimension C which is then stereoized and goes into 2 Eventide H9s to stay in stereo for reverbs and delays, and stereo in to a mixer. I've also got mixer sends going out to a Strymon Bigsky and a Roland Re-201 tape echo. All that to say the sounds are extremely stereo and wide if I want them to be.
But, on its own, the sounds the Prophet 10 makes are just amazing. The factory presets do an incredible job of showing how many different types of sounds are possible from a fairly basic architecture. I feel like the entire thing is a sweet spot. I'm adding this to a Moog Grandmother, as well as a Mother 32, DFAM, Subharmonicon, a Behringer 2600, a Korg OpSix, and a Nord Modular G1. I feel like my bases are covered. The only thing I need now is a replacement midi controller and I'm hoping Arturia or Novation come out with a new 61 key model soon.