655 is a good pump and is easy to use as it is already to go with a molex connector.
But there are much better pumps availible but require 120v
you basically can get them to turn on with a simple relay and they also make PCI controller cards as well
Ehiem 1250 is a great pump for a PC ... it is rated around 500GPH and has a better lift than the 655 ....
So it really depends on the lift and drag of the system to get a pump that will preform up to exspectations ..... many times it is the buyer not knowing the specification on the pump that results in poor preformance ...
Ehiem also makes much stronger pumps as well.
For really insane type stuff TACO 008B Bronze circulating pumps kick some serious booty but at a high cost
They would be pump that you would use if you wanted to put a coil in a remote location ..... Such as an out door coil to use winter temps to you advantage .... obviously this type of application would require an a glycol solution to prevent freeze ups
Best of luck and if you are doing just a small loop internal just use this
qwick and easy
http://www.sidewindercomputers.com/swmc12vdcpuw.html