No, I do not use a downloaded, so cannot comment. Probably one reason you've had no responses, the other is you need to give people time to find and read your thread. We're from all over the world, it does take time for threads to be read and responded to. BTW, forum rules say you cannot bump your thread until at least 48 hours have past.
Back to topic, I've heard more about AVPlayerHD than Buzzplayer. I would be using AVPlayerHD if I didn't have OPlayerHD. They should both work solidly with the formats you suggest.
In regards to downloads, I generally download to PC then sync to iPad or put on the portable drive. If you're using the Seagate, it will be much easier to manage the files via PC.