I have a great respect for F-clef instruments (have played and do play a few myself) and just bass in general, so I'm naturally attracted to it...but I find that quality and accurate representation/texture is becoming the higher priority. I still like my signature to be warm and weighty, so I guess you could call me a basshead in some ways
but it's not just about the bass with these...I think they are pretty great overall. I guess by fun I mean more lively than a neutral signature (of those I've heard) - they are more aggressive but not overly so, they have the bass weight and treble sparkle without a large compromise on the midrange, and they're quick. The mids are indeed nice and the recessed areas really only compromise a few songs I listen to (>10%), but that doesn't make them un-listenable or un-enjoyable by any means. Every headphone will have it's trade-offs, but I value these greatly for what they bring to the table. Are they a means to an end? Perhaps for some, but they're still hard to beat in most respects for their price range.
Less 'Sennheiser veil', more 'Sennheiser presentation'
. I bet there are a few tracks/genres that still sound great if not better on the HD580 - sometimes that laid back presentation is necessary. I have a friend that had a pair a few years back and loved them as he mainly listened to acoustic/folk rock. You seem to have a good collection going so far!