I would get the Ref 31 if you plan to limit yourself to used since it sounds great and the bass notch filter is a big plus in many systems. However, it would not cost that much more to move up to the Rotel 1068 which is a substantial step up from both of your other choices in terms of sound and features. If you are going to keep this setup for two plus years, the 31 would be a good choice but lots of times people make a choice based on saving a few dollars now and are shortly unhappy with it and sell it ending up spending more than they would if they had originally bought the more expensive unit.
