Best Buy, Circuit City and CompUSA have had some pretty good prices on 4200 systems but it looks like CompUSA has raised the minimum configuration on their newer 4200s so that there aren't the old barebones desktop systems.
Circuit City still has the old HP barebones desktop but it's web-only. It still looks like AMD is having no problems selling what they're making and I don't see any really great discounts. They have processors in a whole bunch of segments so they just sell you whatever your segment is.