I always follow these threads because I was wanting to replace my dart with a reliable return dc pump. My reasoning is not power, because most DC pumps above 3000gph really don't give that much power savings for the money TBO over a dart, but most of them are dead silent....so that is why I was looking at them. My reef in in my living room.
In reading the feed back here, you are not going to get the reliability that you already have now. The verdict is out. The pump I was recently looking at was Current USA eFlux DC Flow Pump and it did not get the love that I was hoping it would get as well. As others have said, if you get 2 of them, that will reduce the pressure of having to rely on it. Make sure your apex will tell you immediately when you have a problem should it fail.
Heck even the 2 top dog DC pumps that cost around 2K, which I refuse to pay have had allot of issues as well. I followed that thread here as well. Lots of over heating isssues and replacements on the Abyzz. They seems to get it worked out in the thread but wow.....for that much money. The same thread had some reviews of the red dragon as well and they seemed fairly well, but then again you almost at 2k.
I would probably stay where you are at if it was me. Obviously that is what I have done. I think I will wait a few more years to see what comes out and what improvements have been made in reliability. Most of the DC pumps that people are using successfully are being used at around 30 to 60% power for effective long term use. That includes the big boys as well. From what I read, it keeps them running quit, cool, and without issues.
So if you were to go DC. I would recommend running 2 dual DC pumps on your system both rated to run entire tank and manifolds if one has to run on their own and plumb the system so both can share the load and if one fails you can ball valve the broken one off and let the other take over until you get the replacement. May want to have at least 3 of the pumps for this layout. 2 running and 1 backup. I think you will get longevity out of that configuration. I don t have room for that design right now, but will go that way when I do go DC return.