I have the SA8004 and it's a very nice player. I also have an airplay streamer, but this really requires a server to be running 24x7 for convenient access.
Managing / acquiring / backing up / constantly powering that much storage is not without considerable cost. Considering the original players in question are about 1K and hard drives are quite pricy right now. Unless you are using a low-power machine like a mac mini / HTPC or a small NAS this may increase your power bill significantly.
While I have all my audio ripped, I don't find it quite worth ripping my entire movie collection. TV shows --maybe, but not infrequent blu-ray movies. This is especially if you don't access all of the media on a regular basis. Though it is nice to flip through all the covers in your collection.
They are both excellent players. It is hard to go wrong. If you are going to use the player in a dedicated 2-channel I would get the Marantz and consider a matching amp. If you truly need a universal player for the home theater / living room, I would get the Oppo.