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A dual loop really isn't necessary, but it's certainly an option. The temperature variation within a single loop is actually very small (i.e. within a fraction of a degree celsius), unless you have an unusually low flow rate.
BTW, the tim Allen pump would hardly qualify...

Here's one that's really overkill:
http://www.gouldspumps.com/cat_pumps...atid=76&step=4