I liked my Beyerdynamic DT100 for gaming, shot many times someone through the wall in CS:GO just hearing one mistake step in some direction. But all the weapons sounded like *****, because you could hear all texture/detail/harshness with them and no bass.. That would sound bad since every studio headphone manufacturers goal is to create a headphone that is transparent. K240 is the best or one of the best headphones in musicality at their price range though.
Acoustic damper it's the sticker that says "do not remove" in front of the driver?
You could try some 15-band eq (I have one in my MusicBee player) to eq the bass it has 32hz, 50hz, 80hz and 125hz settings and see if you can lower any of those without affecting the double bass too much? Or try increasing some 100hz punch while using the velour pads.
I found this. "19. Don't put nearfield monitors on their sides (unless they are dual-concentric types) as the sound from the tweeter and bass/mid unit will move out of phase if you move even slightly from the exact centre of the sweet spot. Sideways monitors may look trendy, but they don't work nearly so well as setting them up properly." http://www.soundonsound.com/sos/sep98/articles/20tips.html
Superlux HD668B - if you want to be cheap. semi-open, good transients bright sound.
Sennheiser HD558 or 598 - open, lush sound, a bit more comfort.
AKG K240 - semi-open, Also nicely priced, nice natural sound, very comfort with velour pads.
edit: added info