i just dealt with Trevor from visualdynamics.ca, great guy, great product, and awesome service. He came out to meet me after office hours so I could pick up my kit
AND he offered to install it for free. He also tested each bulb before he actually sold it to me, just another small but important gesture...
Tony the Tiger also bought 4 kits from the guy, which has to tell you something about his reputation and customer satisfaction.
I havent dealt with Xenondepot or know anyone that has, so I can't tell you anything first hand.