Back before choke tubes were everywhere, and you could still shoot lead at waterfowl, upland guns came IC/M and waterfowlers came M/F. For upland, a good IC/M is still one of the best combos out there. While it might be a tad tight for preserve quail over pointers, using lighter loads with a spreader insert will work just fine. Over on another shotgun forum where the focus is more target/hunting oriented, the Master class shooters in sporting clays all seem to be doing one thing - putting in tight chokes and leaving them alone, so it's not necessarily a bad thing.
Personally, I view a 20 as a great upland gun. Depending on your quarry, I would just open them up a little - maybe to IC/M - cheaper than tubes.