Thanks for the recommendations, everyone. Right now I might consider these, but they all have potential flaws that other users have reported, so I'm still in the process of sorting everything out. The flaws that I'm mentioning here have all been reported by other users:
Denon AH-D2000 - I've read the build quality isn't so great and too "plasticy" like the cheaper sub-$50 Sennheiser's, which is a turn off because I want my new pair to last. Some say the bass is a bit too pronounced as well, but it's hard to judge the severity of this since many listeners have different tolerances. Also read that this drives easily without an amp, so I don't know how much of an effect my amp will have with this.
Audio Technica ATH-AD2000 - I've read positive things about this, but this may not sound well with beat-driven music, or techno/deep house. Might be geared more toward softer or acoustic music, not sure.
Sennheiser HD600/HD650 - Many people seem to prefer the AH-D2000 over these from the comparison threads. I also may need to buy a separate cable from moon-audio, ZuCable or Stefan Audio Art and balance them to make these worth my while, but this probably applies to all headphones. I'm also used to closed-type headphones, coming from the V6s, and I don't know how I'd respond to the openness for my preferred type of music.
Audio Technica ATH-A900ti & Beyerdynamic DT880/990 - All these look comfortable and I read a lot of positive things, but a lot of previous owners seemed to have had upgraded to the headphones I mentioned above for some unknown reason, which I'm still trying to figure out. But some have mentioned that the bass becomes a bit muddied or distorted for certain types of music (probably techno?) for the BD DT models.
I am trying to find more info about the Ultrasone ProLine 750 now, since
this user and e-dub claim it's good for the type of genres I listen to, but I read some conflicting opinions on how well these pair with amps, which is partly the reason why I'm purchasing new headphones, to match well with my Predator.
Here are a few flaws that I found so far:
http://www.head-fi.org/forums/4039179-post3.html
http://www.head-fi.org/forums/4012235-post8.html
http://www.head-fi.org/forums/4008769-post26.html
Decisions, decisions... too many conflicting opinions.