If your Oppo has usb 3 capability, I would get one of the Western Digital usb 3 drives. You can get a 2 TB for around 150 and the drive is the size of a deck of cards. I use a 1TB usb 3 drive in my system. You can rip all your music to flac and have room for probably 100,000 songs. The quality is excellent.
Hard drive for Oppo 105 and Sonos
I'm thinking of doing Sonos or something like it and want to start the process by ripping all my CDs to an external drive (that'll give me a chance to decide on Sonos or other similar system while getting the rips done). I want the drive to be compatible with both my 105 and Sonos so when I want I could use the USB connection direct to the Oppo 105 and also have the drive on all the time so it could be accessed by Sonos (if this is possible). What drive would make the most sense for my needs?