Congrats on the new Reefer 250! I recently got one myself and it is a great aquarium.
My previous tank and equipment was too loud for my liking and this time I wanted to focus on buying quiet equipment. Right now the loudest thing on my tank is the skimmer and even that is just a slight hum from the cabinet. Here is what I have with some comments.
Return pump: Reef Octopus VarioS-4. Dead silent, seen other owners go with the 2 and 6 models as well.
Skimmer: Reef Octopus Essence S-130. Great skimmer, might be a tad too large though.
Flow: MP40 x2. I started with one and just couldn't get flow to all parts of the tank unless I cranked it up, which would move a lot of sand. Two paired are working great for my mixed reef. I slightly wish I went with MP10s though. Some owners said they couldn't get them to stay on the glass, but I wonder if they were just using the wrong spacer. With a LPS and softy tank, you won't need to go crazy on the flow.
Lighting: I ended up going with the Deluxe version of the Reefer which came with two Red Sea Reef LED 90s. I'm really enjoying them so far. The Reef Beat app is easy to use, they are small and quiet, and the recessed lens housing helps hide a lot of the light. Great shimmer too. You'll have no problem growing what you want with these, but they could grow some SPS too if you ever decide. Plus compared to other 90w LEDs on the
market, they are pretty fairly priced.
ATO: I went with the Tunze Osmolator 3155 after using the stock ATO for a few days. It works great and I went and bought a 5 gallon reservoir to pair with it.
What I wish I did: There should be a build thread or two where they removed the filter area of the sump and put installed a roller mat instead. I really wish I went this route because filter socks are such a pain.