I seem to have killed lots of ring necks. I've killed some read heads and a few others but ring necks seem to account for the majority of the divers from my hunting the last few years at least.
Let us know how monroe goes for you, never hunted it, but thought of it.
I think those will serve you well. Really buying something specific like that is great, then if you wanted to throw in some of the "diver or puddler packs" that have 3 or 4 different species for good mix serves you pretty well too. Honestly around here I wouldn't be afraid to put out puddle ducks in your diver spread. I see wigeons, gadwalls, and mallards mixed in with them all the time. For some reason I've been finding that often times larger numbers of decoys has been working well to get them to work more so than just "the right kind." Sometimes 12 and a jerk cord is great, other times having 24 or 30+ is the ticket.