I'd also recommend staying away from DC return pumps. There's nothing inherently wrong with a DC pump, and in principle they can be more efficient than an AC design because the impeller will only turn one way in a DC pump, and can have a more efficient "boat prop" form factor than the typical "works both directions" AC submersible pump design. The issue is that all that seems to be available for the hobbyist is either Chinese manufactured pumps of questionable quality and reliability, or extremely expensive German manufactured pumps.
With respect to your application, there's no question that eheim universal hobby pumps have a well-deserved reputation for being bulletproof and incredibly long-lasting (I have a 1250 that has been in continuous operation for more than 10 years with the same rotor).
But in my opinion, a 1260 is really overkill for a 40g breeder. It uses 65w, and produces 640 gph at zero head, with a shut-off head of 12 ft. For that size tank, I'd use a 1250 if you wanted to stick with Eheim's universal hobby pump line. Perhaps a better choice from the standpoint of absolute silence, low wattage and still maintain high reliability operation would be the Sicce Synchra Silent 1.5 - 25w, 357 gph, 6 ft shut-off head. You could also consider going with the Sicce 1.0 - 251 gph @ 16w, shut-off head of 5 ft.
If you want extra flow for reactors, I'd suggest buying a separate Sicce 0.5 - it has more than enough flow for 2 TLF phosban reactors, uses 8w, and allows you to service the reactors without having to shut off/valve off the main pump. In an emergency, it could also be used as the return pump for the tank until you got the main pump fixed/replaced.