They really need to let the market dictate Duren's price. I don't think they will because "player relations", but they should.
Signing Ausar to a friendly contract this summer would be huge. His numbers are just going to get better as his minutes increase (they better increase) and he improves. But more than likely he's going to make an NBA All Defensive team and I'm guessing he won't sign for cheap.
I'd be happy with bringing Harris back as a backup PF. He's fallen off, but still a smart player, good in the locker room, and would be among the league's better bench players, imo. Depends on the cost though.
Their needs: To me, it's 2-way players. You can't keep running out guys like Robinson hoping he's hot enough from three to make up him getting targeted on defense every time down the court. Unless Ron or Ausar magically learn to shoot, they've got to replace Robinson and Harris with 3-and-D forwards.