Interesting.
For some reason, I don't see him going to Houston. I think the Rockets are pretty set and if anything, they would need Josh Smith more than DH to play the 4 with Asik at the 5 and Harden at the 3.
Dallas is definitely a good fit! Also, what's intriguing about Dallas is (correct me if I am wrong) don't they have enough cap space for two max players??
If so, then CP3 and Howard teaming up becomes a reality. Then, you'd have your new super-trio with Paul, Howard and Dirk.