Im of the opinion that the 10x turnover rate is ok if you want to go that route but its a bit old school. When those numbers were brought about you have to remember that we didnt have all these high powered powerheads and wave makers like the tunze, vortech, and now the wp40/25s. Most if not all the water movement in the tank was via the return pump or closed loop system. Water flow/movement via the powerheads i believe is more crucial than the turn over rate through the sump.
Alot of people as a matter of fact like a lower flow through the sump because it allows longer contact times in the fuge and skimmer area. I for one am still running an old mag 7 which is about 700GPH. I have a 80 gal tank with 55 gal sump and about 10 gal quarantine/frag tank plus the 15 feet or so the water travels from the sump to the tank(people that have been to my place know what im talking about) so im running well below the 10x turnover rule.
Im not saying it shouldnt be done, all im saying is that you can go with a smaller return pump to reduce noise, heat, power consumption, ect. You dont NEED and 3100GPH pump. If you want to, and dont mind the larger power draw or want to "T" it off to other devices like a frag tank, reactors, UV, etc then yea it makes sense.
Then again, with the variable control pumps now, that kind of gives you the best of both worlds huh?

I might be looking at getting one of those for my next pump.