I've always found Harden to be overrated. He's terrible and lazy defensively. He's been downright horrendous in the (small) 2 game sample this postseason. The previous postseason, he averaged 4.5 topg and shot below 40% from the field, despite good point totals. Most people are familiar with his chokejob in the 2012 finals.
But I know I'm in the minority and most fans still value Harden pretty highly as a basketball player (some even a top 10 player). Maybe NBA teams do too.
I know people are low on Carmelo, but I think he's a better option alongside Dwight than Harden. My roommate disagrees.
So Carmelo for Harden... who says no? (in the literal sense, not the wanna-be-like-Bill-Simmons sense) Try to disregard that Houston already has Parsons at SF and NYK has a logjam of SGs. Assume that other pieces could be added to the trade or a 3rd team involved to help take care of that.