I run a 512 gig usb on my 6700 and 8015, I had issues, missing songs, crashes and sluggishness. I have spent the past month redoing them. They are now flawless, 1200 FLAC CDs on both, I can access either USB from either receiver so I divided them by artist, A-N on one, O-Z on the other. Long ago I read that Denon Marantz did not like inbedded artwork over 500 pixels and noticed that one's over 1000 x1000 would cause tracks to not show, sluggishness and crashes. I used tagnrename to reduce all imbeded art to 400 or less if all ready under 400. Unfortunately I could not find a way to do it in bulk, you can do it folder by folder to do one full CD rip with a couple button presses. I did weed out junk in the folders too, if you reduce all inbedded art to 500 or less and only have the songs and a Playlist in each folder things really speed up. I can now scroll from top to bottom with absolutely no pauses or sluggishness, even if I am reading the other recivers USB. Everything is in the right place, no more missings or unknown artists. I added about 50 at a time after I was done, if at some point I had unknowns that were tagged right, chrashes or sluggishness I jacked the USB stick back in the laptop and sure enough over and over I had missed shrinking inbedded art in a folder, normally about 1400 x 1400,just had to shrink it and all was good.