Really necro-posting, but I'm in the process of rebuilding my centrifuge system at another location.
Short answer, buy the single-pass system, with every performance-improving option you can. Inline heater, bigger rotor, anti-splash feeding cone, etc.
I've been using a drum heater on a 55-gallon drum (insulated), 4gpm hydraulic pump feeding a Spinner II 76SE. There's a manifold with a temp/pressure gauge & adjustable pressure relief. Works well, but heating the whole drum up from 55degrees takes several hours at best & I've been running it for long cycles, with cleanings between cycles. Hopefully I just got a couple of bad batches.
24hr runs at 150degrees & 90psi. Centrifuge is rated 2.5gpm at that pressure. I cleaned a 1/3-1/2" layer of fudge out of the rotor for several days in a row before it started to reduce. Please note that my rotor is a lot bigger than the little 1gpm units.
Final filtration before going into the truck is a wix 1-14 filter head with a 3micron water-block filter, same as my filter on the truck.