Just to be clear, to those who mentioned Tim Sylvia, while Timmy Chonga may well be debuting in Dream on March 22nd, he will not be fighting Josh Barnett.
His management turned down the fight with Barnett already.
I'd like to see that matchup, too, personally. But the reality is, Tim needs to get some confidence back before he steps in with someone who's a legit gamer. Despite the steroid use, Barnett's a legit gamer.
The problem with Dream right now is that they don't really have any legit heavyweights for Barnett to fight. Their heavyweight title is vacant and their "superhulk" champion is a middleweight who, lets face it, would be horribly murdered by Barnett if the two ever fought.
All of the good fighters who'd be a test for Barnett who might have ended up in Dream are currently on the Strikeforce brand. Arlovski, Overeem, Werdum and Antonio Silva all make for interesting fights with Barnett, but the chances that he's going to fight any of them in the near future seem pretty slim.
Honestly if you take all the people you mentioned out of the equation the fight I would most like to see is a rematch with Jeff Monson. There first fight was fairly close (I'd give Monson the first and Barnett the second and third.). There is Sergei Kharintov in Dream though which could be a decent fight.