Following along too ! I was so impressed with these Red Sea Reefer tanks that I had to grab a 170 to try out for myself (actually have your old Kessil 360we on it !) . So far, I really like it and yes, it will be very quiet ! Its quiet enough for me and I am kind of a stickler on my tanks being , well ......... very quiet !
Good call on the 3155 . The only short coming on the Reefer tanks is that useless Red Sea top off system. I re-purposed my red sea top off reservoir into a refugium (pics are in the Red Sea Reefer thread) .
I would caution on using the main pump for anything else but a return pump. Even the slightest variance in pump pressure for any reason ,even barometric pressure changes and water level that the pump is running in, will change the pump flow ever so slightly that it will be hard to keep the tuned overflow adjusted perfectly . Adding reactors to that , will just compound things . Try it ..........but you may have issues keeping the tuned downflow adjustment rock solid.
Other thank that ..........your equipment list looks impressive. That AP 700 should be a perfect match for that tank.
Good luck on the build !