I've been over, around, under, and through with headphone rigs for bass: The old Yamaha 'Producer Series' stuff, the Raven box, you name it. The little stuff was always let down by being battery powered and/or they'd only drive $10 headphones.
Finally I quit fooling around, bought a Mackie 1202 mixer (the newer style with the VLZ inputs) and serious Audio Technica headphones, called it a day. Can not crash the inputs, the A-T's let me hear anything, and you can mix anything in or send anything out. Put a tube preamp with a good XLR out inline, and it's just the best.