Sennhesier HD650s > DTS/DD Amplifier > Onboard sound over Coax S/PDIF (digital connection)
HD650s picked for good quality, clean stereo sound in a lightweight, super comfortable. Yes it's a 200+ headset but they have lasted me for years and years, would never go back to budget/cheap cans. Only consideration should be when listening around others, open design = some sound leaks.
Amplifier as you cannot run the above from on-board sound. Exceptional clarity. The DTS/DD does a far better job of pseudo-surround than any 5.1 headset I have ever used. Stereo reproduction on a quality headset is just far better IMO.
Onboard sound - Using a digital connection to an amplifier which does the processing. Zero gain for me getting a better soundcard. If I was using my headphones directly into a card over a purely analogue connection then I would absolutely invest in a dedicated sound card.
No mic on the HD650s obviously. I use a USB desk standing mic. The digital transport nature of USB has been FAR better than any analogue connection I have been able to get with my systems, probably due to onboard sound and silly levels of interference. It did present problems in that standing on the desk you type on = vibration = TAKATAKA noises. I've since No More Nailsed it to the wall
My out and about/laptop/travel choice is a set of Sennheiser PXCs. Absolutely excellent active noise cancellation in an over-the-ear foldable design. Best money on a travel product I have ever spent. Removing that low drone of aircraft and otherwise is <333333