Hi Richard,
The size of the medium card/device will depend on what format you have used to transfer your music collection on the B2. In terms of brands, I only buy from reputable suppliers such as Argos in the UK or Best Buy in the USA. I avoid Amazon and the web offerings because much of this stuff is absolute rubbish and will cause much pain. If the device is cheaper than a reputable supplier then is is usually fake. There are quite a few threads in this forum where many problems are reported and often it boils down to a cheap USB device.
In terms of device size:
If the collection is uncompressed & stored in '.wav' format then your collection will require about 250GB, so a 500GB device would be advisable.
If the collection is compressed to '.flac' format the the collection will require about 150GB, so a 256GB device would do the job.
If the collection is compressed to '.mp3 256Kb' format then the collection will require about 50GB so a 64GB device would be adequate.
If the collection is compressed to '.mp3 128Kb' format then the collection will require about 30GB so a 64GB device would be adequate.
If you post here the 'Settings & Status' screen from the WebUI, this would give an exact count of the tracks in each format, so a more accurate estimate could be given.
With regard to the type of device to use, that depends on your situation. For example, I have three cars, but only two have the 'SD card' slot, whereas all three have a USB port, so I use USB sticks.
Also, you need to check that your vehicle will play the format(s) that you intend to use. Again, in my case only two of the cars will play '.flac' whereas all three will play '.mp3' format, so I use the B2's 'Export mp3s' function.
The process to transfer the music to a USB device is fairly straight-forward.
1. From the front panel 'Main Menu' --> 'USb Menu' --> 'Export C' -- this copies all of your music folders to a device plugged into the USC C port on the B2
or
2. If your collection is in '.mp3' format you can use 'Main Menu' --> 'Playlist Menu' -- 'Export mp3s' but first you will have to create a playlist than contains all of the artist/ albums that you want to transfer.
Regards,
Peter.