Loud hum on circulator pump

Having asked before and not getting an answer, I thought I'd try again:
I have a Buderus boiler with a Taco 0010-F3 circulator pump for the heat. There are 12 zones of baseboard and 3 zones of radiant. Each radiant zone has it's own circulator, plus there's one more for the hot water.
The main circulator hums, although it seems to be working just fine. Can any of you HVAC guys recommend a better circulator pump for the baseboard heat? I'm looking for high quality, but less hum.
Thanks,
--
Larry
Email to rapp at lmr dot com
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I converted two systems with big old Taco external-motor pumps to Grundfos and both became so silent that the major problem became knowing if the pump was running or not. As a side benefit the new pumps were more efficient so they used less power. In my relatively small homes I ran the pumps at the lowest speed for most of the year and only switched to the medium speed during the coldest part of the Alaskan winter.
http://www.grundfos.com/web/homeus.nsf/Webopslag/786D642D1BE05951C1256C3D002E7FA6
--
John McGaw
[Knoxville, TN, USA]
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wrote (with possible editing):

Thanks, John,
    I'll give them a try.
--
Larry
Email to rapp at lmr dot com
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