At this point, I think Harris in Orlando and Noel in Philly are our best bets.
DeMarcus is a pie in the sky scenario. I agree with others that he's not getting moved for at least a year, possibly not until there's one year left on his deal.
Melo could be available for trade in the near future, but trading for a 32 year old Melo would require us to immediately jump into contention mode, and I don't know if that's really plausible.
Trade for Harris and Noel without giving up too many assets and we could have an interesting young core that is just one or two pieces and a couple years of experience away from being really good.