Am I correct in that you can't record an outside source to the 921? I hooked up a source to the IMPUTS, while I can watch the source via Channel 0 (AUX) I cannot record?
You are correct. The 921 cannot record from the aux input. It also cannot record from analog OTA channels. To do so would require the 921 to have a real-time MPEG 2 encoder which the 921 does not have.