I'm using a dc10000 for my closed loop. Here's my layman's opinion.
It's very quiet. Can't hear it at all.
I don't like the connections, I'm using 1-1/4" flexible tubing, I think, because you cannot attach PVC to the threads that come on them. I was bummed about this at first, but now that I'm using flexible I don't so much mind, I can move it around a little in the stand to get to stuff, etc. The new dc12000's are supposed to have PVC type of threads.
I had some problems with the electrical connection on the controller, and it took them forever to get me a new one. Eric at OBD really had to get tough with them. I was having trouble getting them to answer my emails, then all of a sudden they'd answer one at like 11PM! I think there customer service is lacking.
I'm using mine with two 1" lines into the tank. Each of those is split into four 3/4" loc lines, so 8 outlets all together. I wish I had a little more flow, but it's not bad. I'd really like to get an Oceans Motion to vary the flow from one rock pile to the other, but I don't know if I've got room in my stand. Plus, I don't want to spend the money now.
I don't worry about the multiple speed settings, I just have it on full blast.
Since I only have 1 of them, I see no need to have the apex controller capability. If you have more than one, then I think that would be cool.
Overall? I like it, but I may get a bigger one when they come out, or supplement with the Oceans Motion.