Are you concerned about noise and what is your budget?
-MCP650/PolarFLO TT is same thing (but different bling factor) and may be found to be noisy
-Eheim may be on the weak side unless you are prepared to run 2 in series?
-AquaXtreme 50Z-DC12 looks like your best bet, although reliability may be questionable? considering that Swiftech stopped selling the MCP600 which is the same model.
-Also Iwaki if you have a deep enough pocket (not sure of model number)