I'm suppose to have a 622 install tomorrow and from what I understand I can forfeit the $100.00 rebate for my 921 and keep it. I have a 501 and was thinking of replacing it with the 921 in the event that I get an in-expensive hdtv in the future. I also realize that I would have limited hd coverage on the 921. did anybody else keep their 921 and use it this way. thanks