Hey Tom,
I've used Smarthome, and
HomeAutomationNet.Com. On some items one has the better price; on some the other place has the better price. For example, Smarthome has the IR-543 controller, which allows me to use my MX-850 remote to control my lights, for $30. HomeAutomation has it for $20.
I recommend using either source to find the item(s) that interest you, and then doing a google search to find the best price on each item. Ray did this and came up with a site that was closing out it's inventory, and we got some controllers for something like $3 apiece.