I have a four receiver setup. 510 just shot craps and DN says I can't downgrade - which sounds completely bogus (they just don't want to cut loose of the $4.99 per month DVR fee). I also want to replace two old legacy receivers (2800's I think) that cant hold a signal. I can get, as a bundle, two used 301's and a 508 for cheeeeeeeap. They are guaranteed to have no outstanding balance. Are there any other concerns I should have buying used receivers such as activation from DN, etc...? Can I use my existing cards (the 510 card and each 2800) in these replacement receivers? If not, how do I get replacement cards? Anything else I should be aware of? I just can't seem to trust DN - you never get a straight answer if there is some chance you might take a dime or two away from them.