Pho I largely agree with what you wrote. IT and Crowder are the most valuable as of now; Sully is disappointing now, esp. considering this is a contract year. But as you, in the final analysis all depends on what the return of a potential trade will be.
Just two things, I value Amir more than you suggest. I mean, we all know he is p old, but Amir is quite valuable to us now, probably more to us than to most other teams. Ofc it all depends on both sides agreeing but given that he is a good fit (and there doesnt seem to be a great demand for him) I don't see many reasons for him not to stay.
Also, we have a certain shooting guard named Marcus Thornton somewhere in Australia. Sure, he is not our greatest asset, and he is already 22 yo, but there is a small chance something will come out of this. My impression is that ppl would pay more attention to him if he played in the D-League (cf Mickey), but there are plenty of cases that 45 nr picks were converted to serviceable NBA players.