Muscovy is my favorite nation to play -- so many interesting options. I'd agree that quality ideas are nice to have -- you won't be wanting for quantity, that's for sure. I'm in the 1700's and I have over 500k manpower. Turn those endless hordes at your disposal into decent fighters and you'll be an unstoppable military machine.
The reason you might want quantity on Russia is because Quantity + I think Administrative with the build cost reductions in both Cost and Monarch Points makes it amazing for countries with tons of provinces that need to be upgraded to be worth a damn (aka Russia).