Back in the day the Quiet Ones were a pretty good pump butthe ysuck today. I had a 4000 literally burn up, flames, sparks and all on my 100G mixed reef. I stuck my hand in the tank and it was hot to the touch and I felt a tingle.
I thought it was a fluke so while waiting on a replacement, out of warranty of course, I used my Ocean Runner 3500 spare. The tank temp dropped 3 degrees, the tank was quieter and my power consumption dropped 13 watts while the flow increased. I reinstalled the new 4000 and the temp went back up anhe power went back up. I also found with both the old an new that they had trouble restarting in a power outage. It went in the trash.
I also had a Quiet One on my calcium reactor as a recirc pump. One day I opened my stand to add water to the sump and was squirted by water! Turns out the motor housing cavitated or developed a hole right through the mte windings and was filling my stand with water.
I wouldn't wish a Quiet One on my worst enemy. They did not acknowledge me when I contacted them and their pumps are garbage.
I would suggest a Water Blaster, Eheim, Octopus or Ocean Runner if you want a constant speed AC pump or look at some of the new DC pumps that are variable speed/flow.
I did a big write up some years ago for Reef Central back when I was part of Team RC on pumps and tested many of them available at the time for heat gain, power consumption, ability to ump against head and noise using a dB meter and Quiet One and Mag were low on the list.
Ocean Runner 2500, Eheim 1260, Water Blaster 3000 all come to mind. All seem to be conservative on their published pump curves so pump a little more and to a higher level than their graphs show in my experience.
Why are you wanting external? Is your sump drilled for an external pump? Do not attempt an up and over pump suction since this is a disaster waiting to happen in a power outage. Submerge the pump in the sump or drill and install a bulkhead so the pump has a flooded suction for reliability. The heat gain is the same either way with any of these pumps since they all use tank water flowing through internal water jackets of passages to cool the motor.
The sump I have is predrilled with a bulk head , (that up and over thing sounds like bad news, and I would never !) thank you ,, after reading more I am now teetering between an eheim , or a danner supreme mag 7
Read my last sentence in post #2. Mags run hot, draw more power than comparable pumps and have noise and rattling problems. The design has not been updated or changed in 40 years so they have not kept up with hydraulic and electric motor research and development while others like Water Blaster are pretty advanced.
I found my OR3500 to be slightly more efficient than the comparable Eheim 1262 as well as the OR2500 vs. 1260 but the Water Blaster is much more efficient and will pay for itself in power savings in a year or two at most. The new DC pumps such as the Jebao DC series do not have a long track record but look very promising and very cost competitive.
Did you use a Kill A Watt meter or a digital thermometer on them? How about testing the flow rate using a flow meter, sound with a dB meter and the head using a calibrated 10 psi pressure gauge and a valve to simulate head?
Not being argumentative but actual testng under controlled conditions showed otherwise. This is based on data not opinion if that matters.
Mine is not opinion, it is based on side by side testing with similar sized pumps under the same conditions. They were bottom of the list among Eheim, Ocean Runner, Via Aqua, Mag, Rio and Rio Hyperflo and others I have since forgotten. If I could get on RC I could find the data to back it up. The testing was quite extensive.
I have a brand new Mag 5. Bought originally (against advise) as a return on my 40B. It's now sitting in the bottom of my 32g mixing brute. It is loud! Heat wise well I don't need a heater in the brute seriously!
I was given a Sicce Syncra 2.0. (Thanks mfinn) and this pump is awesome! Quiet and powerful