Awesome, that's the same size as my tank! I believe in low turnover to the display tank because it's quiet. I do ~75 gallons per hour. That should turn over "all" of the water a couple of times a day. I can formulate no logical argument requiring more. My return pump feeds 4 tanks and is soon to also feed a chiller. It is gated back on each of those returns and has HUGE head loss running around at least 6 90's getting into the house from the fish closet to feed the water change chamber and the display tank. I can still overflow the display tank if I open it up all of the way. Cool pump.
Interestingly, if I dose alk into a chamber in the garage, the alk changes in the display tank within a 2-3 hrs, but this also ensures slower changes in the display tank which is safer for everything. Think about it, right, I can overdose Alk accidentally into the skimmer tank in the garage and it not only needs to overflow into the sump, but then be pumped into the display tank -- safer.
Flow in the tank on the other hand, completely different story. I have a Tunze 6100 in a 30 gallon frag tank and I'm still suspicious I have dead spots and I'm thinking about adding a K4 strategically. I don't get people with 50 gallon tanks who want to trade a K4 for a K3 because it's too much flow. I had 2 K4's in the tank and it definitely was not enough.
Ron