I took a look at the Virtual DJ webpages. Never knew that DJs had such a wide variety of choices and equipment. Tells you I don't go to many upscale weddings and fewer night clubs :-)
From the looks of the page, the program is file based. As such I would not see any purpose is transporting the B2 around to provide that. Copying the file to the same drive or drives as your existing would seem to make a lot more sense. I also suspect that the DJ software makes extensive use of tags in the files. The B2 will only add very basic tags when you rip a CD so you would have to add and update those tags to whatever standard for use with Virtual DJ. Choosing to rip those CDs on the computer with dBpoweramp or other software could provide you a substantial step forward. The B2 will accept all the music with the fancy tags but ignores the tags. You do have to copy them into the B2 with the proper directory structure and name convention.
My recommendation would be to put the music on the B2 as FLAC files that you want to play and listen to, leave the DJ stuff on the computer or an attached USB drive. If you use the DJ software to create a new FLAC file, you can add it to the B2. You could add MP3s as well.
I don't know how big your collection is. If it larger than the harddrive in your B2 then you must already manage two locations. The B2 expects a FAT32 formatted drive with a maximum size of 2TB. So that is arbitrary limit on your DJ side. I would obtain a name brand 2TB USB drive (name brand so you don't get a fake) for a complete and safe backup to the B2. Then using the computer (do not allow the computer to "FIX" your FAT32 drive, it will destroy your data) to transfer that to your computer or a larger USB drive. My computer is using 5TB for backups (so I can keep more than one) but I bought a 2TB for B2 use. So if the 5TB breaks I still have a 2TB of the music. If the 2TB breaks I can recreate it from the 5TB. Always a good thing as Daniel says.
You could use the audio output but what sense would that make if you already have a FLAC file? The 15W amplifier is hardly DJ material.
Ray