I recieved my 622 yesterday for an install tomorrow and have to return one of recievers as part of the deal. I thought I had two 510s but found out that one is a 501. The problem is I have alot of movies on the 510 and don't want to lose them. The 501 has nothing on it. What is the difference between the 501 and the 510? I have had the awhile and forgot. Is there a benefit in keeping one or the other. I also have and older 1000 model that has been under my bed for about 5 years, can I send that one instead? Thanks