Thanks for the assistance, that helps a lot. Strongly leaning towards the Oppo PM3 right now, mostly because I've heard great things about the PM3s and expect a $400 pair of headphones to outclass a $200 pair. I only wish they were sold on Amazon, so I could use my Amazon credit.
If you don't need them to be portable the Stax SR-207 are without a doubt going to have the absolute best clarity at that range and come with their own amping system.
I think the Sennheiser HD600 might actually have a slight edge in clarity over the bassier 650, but both need to be well amped to sound their best, which is going to raise your total cost.
The Mad Dog is a good closed headphone to consider though they scale well with amping also they're cheap enough to leave some breathing to buy an amp should you need one.
The AKG K712 Pro would be great clarity wise and comfort wise and although they scale tremendously well I don't think they sound too bad unamped.
The Shure SRH1540/1840 is another good suggestion as they both sport great detail have a smaller form factor, and really efficient sounding great out of various sources.
The Beyerdynamic DT880 are extremely comfortable, sport excellent clarity, and offer a variety of different OHMs should you decide you want to be to listen to them straight out of a phone.
The Focal Spirit Classic are really detailed, efficient, portable, and balanced but they're not the most comfortable for long sessions.
I'd also consider shelling out for the HE400i or HE-500 if you're really serious about
clarity. They're not too shabby out of menial sources, though obviously they also sound better amped, but both sport an incredible clarity coupled with such a fast response and decay in comparison to say the HD 650/600 which are both fairly detailed but kind of too laid back to make it apparent.