I used to be an only speaker man seeing headphones as subpar audio accessories, this was 10+ years ago. Since i plugged my HD600 into the Manley 300B preamp i discovered that headphone listening can be quite amazing and this is even more true with the HD650. Dynamic headphones have really seriously improved since the last 2 decades, the purity of tone, dynamics, bass, etc...are simply mind-blowing. There's also an intimacy with the music that is very addictive. An immersion which is different than what you get with speakers.
The technical strength of headphone setup is a very short signal path (no extra cables, power amps), the simplicity as a sonic transducer (one speaker, no crossover), again this gave me a purity that is hard to believe. Only drawback can be a lack of serious depth, normal, you're not in front of the speakers. And the huge soundstage only speakers can provide.
But the biggest 'problem' is that it gonna cost me a small fortune to bring the sonics excellence i got with my phone to a speaker setup. A 300B addiction is definitively not good for the wallet when you want and need power for a speaker setup.