DC has less EMI,
you can connect them to a PWM or Rheo controller,
connects directly to a molex,
usually better than most currently available AC pumps,
check the D4/5,
or Laing DDC.
http://www.sidewindercomputers.com/swmc12vdcpu.html
http://www.sidewindercomputers.com/swmcpu.html
Same pumps, but different versions by Swiftech, Danger Den and PolarFlo.