Of the three, the remora is the weakest choice but is definitely workable.
I'm hearing very mixed remarks about the new deltec MCE300 hang on, and at least one person who remarked that he didn't feel it was outperforming his remora. If you decide to go with a deltec, I'd just go whole hog and get the MCE600 instead.
The tunze seems to be remarkably good for it's size and price point. The negative to it is that it requires mounting inside the tank and is fairly intolerant of much in the way of water level changes.
But you nailed it pretty much, these are the worthwhile choices in that size range.