After reading some reviews on the Q40s, they look like a great option...but that build quality is a bit worrying though, the price might make up for that. I've also looked at ATH PRO700MK2, and Ultrasone HFI-580, not sure about them though...they have good reviews but no one seems to know a lot about them.
Ive had them before. I can compare them to the xb500s, the xb600s and the dt770s (80 ohms)
The xbs sound about the same with the 600s more bloated in the bass region.
Hfi 580 comparison:
Sub bass: less than xbs in quantity and impact, better in quality.
The dt770s beat the hfi 580s in quantity, impact, and quality.
Mid bass: slightly less than the xbs, much quicker and have the tiniest but less mid bass.
The dt770s have about the same amount of mid bass, the 580s have better quality though.
Lower mids: 580s best all by far.
Upper mids(im assuming these are femake vocals?): 580s are equal to the dt770s.
Highs: 580s highs are soooo nice. Love em.
Soundstage: dt770s have the best soundstage, then the hfi 580s but at this price i honestly wouldnt take soundstage into consideration unless we are talking about open cans.
Comfort: dt770s win, then xb line then hfi 580s. Comfort is terrible on them.
Clarity and detail: hfi 580s and close behind dt770s. Clarity and xbs shouldnt be said in the same sentence.
Basically its all about preference between the dt770s and hfi 580s. Dts have more sub bass impact, 580s have more detail.