The 620's are nice but tend to quick working due to Ca
buildup on the shaft. They do move water even though if you put your hand in front, it does not feel like it. Might consider an 820. Most people on RC like them better than the 620.
Only Rio I have ever owned was very loud. Ever consider a Mag?
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,