How did you watch the Amazon Prime stream? In Raspbmc? Or just through a browser in Raspian? Other?
One thing I discovered, the device must have at least .850 amps or you'll have issues. At 1 amp @ 5 volts through the micro USB, not problems driving a mouse, keyboard, VGA adapter and a small set of speakers.
Another thing, you have to go to audio settings, under system settings and tell it to use analog (headphone/speaker jack) or HDMI. It has unbelievable sound sound and picture for a $35 device. I still haven't tried the RCA video output for comparison.