GREQ
Headphoneus Supremus
The 'old farts' on this forum have been using this old trick with the AKG K1000 - released 1989I have to credit @OhMyGodPancakes with this idea, specifically we both have Oppo HA-1's his idea is to from an amp that can do headphone and pre-amp out at the same time, hookup line out to a powerful external subwoofer, so you can listen to your headphones and also have(low volume, just want to feel it a bit) the woofer going to compliment it.... We also both like Audeze headphones, and have 150W+ woofers so this is a killer combo, not to mention the HA-1 is magic!
Also I will add since the woofer is mainly for the physicality you don't need something crazy expensive, a powered one works fine, but you will also benefit from using a high quality dac/pre-amp anyway so there is a sound quality boost but the cheapest kind! Free, to me that is as quality as spending much more on a nicer woofer.
Personally I had fun combining my sub with my Sony VIP-1000, which is a similarly open-air design.
It's good to see the old tricks being revived and talked about.
Goes to show that the best ideas will be had over and over again.