$5000 or under speaker secommendations?

I'm thinking about getting a second, used pair of either bookshelf or full range/floorstanding speakers for my system (currently I have the Avalon Radiants and love them).

Not wanting to spend my child's college tuition on this second pair, I want the best money can get for a pair that would typically list around $3,500-5,000 new. I'm considering the Martin-Logan Aerons or Ascents, Opera Callas, Thiel CS 3.5, and Sonus Faber Electa models, but am wide open to other recommendations.

Anyone care to share their opinions, preferences, favorite picks?

Thanks!