Quietest return pump I've found: Reef Octopus VarioS. For your tank, I would get either a VarioS-4 or VarioS-6. I tested the decibels, no increase from ambient at about 80% power.
I've tried: Eheim, Sicce, Skimz, and Reef Octopus. I haven't tried the EcoTech, but I think those are pretty good too. The nice thing about VarioS (I didn't think I'd ever care for, but ended up really liking) was the ability to control it with an Apex VDM to my Apex Jr., and the float sensor for shutting off the pump for when the water level drops too low.
For a skimmer, I would recommend a NYOS Quantum 120. Pretty quiet and works great for a Reefer 250. I bet there are quieter ones, but I've only been able to try the Simplicity 120 and Quantum 120 head to head. Quantum wins on sound and performance for me.
I've had a bubble king mini 160 in the past, I think that one is comparable of not quieter. Might be a bit overkill for even a 250.