Is there anyway to watch recorded shows from one DVR on the other DVR? I have 2 722k's, 1 in den, 1 in bedroom. Can I record shows in the den and watch them in the bedroom and vise versa? If not, is this what the slingbox is used for? Also, explain the external hard drive...as I understand it...the ext HD can be plugged in on den dvr, record show, then unplug and hook up in bedroom to watch? How easy is it to plug and play?