V-Moda Verza.  I have been in portable audio nirvana with this combo.

D600 vs. PRO900 or SigDJ?  Regardless, I would give the edge in comfort to the D600, although the Sig DJ has a more secure fit for portable use.  I found the D600 would slip quite a bit when walking.   My amp is the V-Moda Verza.

I am familiar with both of those headphones and the answer is a definitive yes across the board regarding the D600.  Bass is closer related to the PRO900 from memory, but I consider their highs harsh and mids recessed by comparision.  The Sig DJ is really in another league, as it should be for...

"Welcome to the grand illusion..."

Glad to offer a good suggestion.  Here is one more- I jammed out to Led Zeppelin for about two hours the other night hearing details I never heard before.  Add classic rock to the Sig DJ's checklist.

While I can't speak to the IEM comparison you are requesting (it is obviously much more challenging to demo IEMs vs. headphones for hygenic reasons- for some reason I just had a vision of a big wad of ear wax stuck to a silicon tip),  one big difference I see between the AH-C100 is the design...

They do lack microdetail, but are highly capable with just about everything else.

The NAD HP50 may be another option to consider.

Push your budget to $80 for Denon AH-C300's and you will be a happy camper.  These were selling for $250 last year.  The WOW factor of the bass and sub-bass on these make them the most fun basshead IEMs I have heard anywhere near their price and the mids/highs are respectable.  They are like a...

After spending months with the Ultrasone Signature DJ, I have come to the conclusion that they are so perfect for me that I almost feel as if they were custom designed, to the point that I can say I have lost interest in hearing other headphones, especially paired with the V-Moda Verza which I...

Comparing my M-100s to my Sig DJ, you are paying for a much higher level of resolution, detail retrieval and an overall cleaner, more accurate, transparent sound and bigger soundstage except for the bass which is elevated.  Friends and family members who are not audiophiles and have compared...

An interesting first post.  I would love the option of wood shields.

I think this may be a result of the thin stock earpads and the XL pads isolate better as I own both.

This is the case I purchased and love it!  It is so easy to remove my phone and place in a rubberized slider case for lighter travel.  The machined aluminum fits perfectly and securely.  For my needs, I definitely prefer this case to the Metallo and it was worth the extra $25 shipping from Japan.

If by too neutral, you mean that you prefer more bass, then the M-100 with XL pads may be for you.

E11 can drive volume much louder than Z0.  Both have excellent bass boost, but ZO offers more bass boost control.  If I could only choose one, I would go with the E11.

Sell everything, pool the $ for the Ultrasone Signature DJ and call it a day.

UE4000

definitely

Choices are limited for what you seek for $100, but you may want to audition the Monster N-Tune which is in your price range and may meet your needs.

I can't believe there are no right angle connectors available in the US.

IMO, their Signature line is worth the price.  I own the Sig DJ and it is my end-game headphone.

If you are dissatisfied with the bass from your M50 and really want to add some low-end impact to your music while maintaining quality mids and smooth highs, then yes.   Since you are in Minnesota, you can probably demo them at your nearest Brookstone.

I never heard them, but they just released the CAL 2 and am reading good things.

I have not listened to the M50 for some time, but from memory, the HP50 just does everything better across the range including a bigger soundstage and comfort.  IMO, the HP50 is absolutely a worthy upgrade.