I just thought I'd pass this along if you haven't already read this elsewhere.
If you are an existing DTV customer, you can call in and ask to speak to the customer retention department. Explain (only if it's true) that you have purchased a Hi-def TV and that you are wanting to upgrade to equipment needed to view it. By explaining that you are excluded from getting the really good deals offered to new customers and that Dish will give you comparable deals for switching over, they will then have some incentative to offer you something to remain a DTV customer.
In my case, they agreed to send (I received in 2 days) me an Oval dish, 2 dual LNBs with a spot for the sat c, and a multiplexer designed to handle the 3 lnb. They even covered shipping as long as I would remain a customer for 12 months only minimum package ($31/month).
I thanked the lady, but told her that the set top boxes were really expensive and I sure would like to get a discount on them as well. She said that they could not give me a discount, but agreed that when I called to hook up my second receiver, I'd get a $100 credit to my DTV account.
Well, that's about it. The idea was not original as others have done the same thing, but I thought I'd pass it along in case anyone missed it.