for those who are building a DMX based system, you may want to keep your eye open for this 12 channel dimmer pack, here in the Uk that are often half the price of the 4 way packs but with 3x the channels

NJD 12 CHANNEL DMX DIMMER PACK on eBay, also, Lighting, LEDs Strobes, DJ Equipment, Consumer Electronics (end time 24-Aug-08 10:11:15 BST)

This one is a 240VAC version, but having looked at the circuit board it is also available in a 120VAC version, in fact it looks fairly easy to convert.