I don't think HE-500 lacks resolution compared to T1. I think T1 is just sharper sounding and makes details stand out more. HE-500 is softer and details are more integrated into the overall sound. As for HE-500 being thick and slow, I strongly disagree with that. I think that they are very fast and full in a good way when properly amped. Actually, I think it's T1 that sounds a little too thin, as do other dynamics, when compared to planars. I think that with dynamic drivers, the extra emphasis on micro detail takes away some of the natural fullness that music is supposed to have. I feel that planars provide a more natural balance between detail definition and body.
As for HE-6, I never liked that headphone. Honestly, I think HE-500 sounds more natural and is just as technically capable. All I heard with HE-6 was more treble tizz and a thinner, colder midrange that made music sound less realistic and less fun. It's not more analytical than HE-500 either, because it doesn't have any more resolution or speed or any other noteworthy technical advantage IMO. I know I may be in the minority, but I can't deny what my ears are telling me. I prefer both HE-500 and T1 to HE-6 and I also prefer HD800, HD650, LCD2, K702 and many other headphones to HE-6.
Regarding HE-500 bass quality, I feel that it is only lacking if HE-500 is not driven properly. Even when underpowered, HE-500 has better bass definition and texture than many headphones, especially dynamics. The better the source, the tighter, faster and punchier HE-500 bass becomes. HE-500 seems to improve more with better sources than any other headphone I've owned. The bass character of HE-500 is a lot more similar to that of balanced armatures than dynamics - the lows are cleaner and more defined than with most dynamics. When well powered, HE-500 is also capable of producing a really immediate and visceral bass impact that most dynamics can only dream of. The superior bass performance of planar and armature drivers is backed up by measurements - check out the 20-200 Hz frequency response and 30-50 Hz square waves of dynamics vs. planars and armatures and you will see that even the best dynamics like T1 and HD800 are slightly lacking compared to many planars and armatures.
listen to HD 800, HE-6 on a well powered amp, TH-900, and i guess you can even add the LCD-2/3, the he-500 still even on a good amp seems to lack full resolution, like theres a smoothness and thickness that seems to prevent details from being full resolved and presented. the HE-6 sounds like HE-500 but without that veil and nicer treble detail and clarity. you probably didn't have a good amp for the HE-6, its anything but thin, its fuller sounding than most dynamic headphones. and even when well driven, the bass still has some aspects of it that just don't sound perfect to me, if wooliness isn't the best word to use, i don't know what is, but i can definitely tell that the HE-500 is a fun headphone to have around, though T1, HD 800, and HE-6 are all better. and even though HE-500 has good impact, it does sound rolled off in the sub-bass.