Worth saving for JH13/16 instead of buying P7/NAD HP50?

I'm still new into my headphone audiophile quest, and ready to take the next step. I went from years of Apple whiteys to a pair of Sennheisher HD 280s that I have had for the last two years or so. I really appreciated the increased detail I got from my music and feel a bit hooked on the whole headphones situation.
 
Thing is, my living circumstances are such that I really need some closed headphones as my primary listening device. Also, I would anticipate that a great amount of my listening will be done portably, so I want something that requires nothing more than a portable headphone amp.
 
I've tried out everything I can get my hands on and the P7s are the best headphones I have heard to date (I've heard great things about the HP50s, but it's tough to find places to audition headphones where I am).
 
My question is, if you were to only have one pair of headphones and for that pair to be your sole listening device, and it as required that said pair be portable, do you think the quality jump from something like the P7s/Momentum/HP50s to the JH13s/16s is large enough to warrant the extreme jump in price? I know that valuing sound quality in monetary terms is highly subjective and circumstance-specific, but given that I may not be able to audition the JHs for myself I was hoping you guys could give me some of your feelings.
 
What do you think is the extent of the jump from P7s/Momentums/HP50s to JH13? The jump in sound quality I'm most aware of was from the Apple stock to the HD 280s and I would consider that a significant jump, not just incremental. To invent an arbitrary scale, I guess I felt that if the Apple stocks were scored 100 I would give the HD 280s about 200-250, despite their obvious flaws. From what I hear in the P7s, to me, I would be thinking something like 350-400. This is just to give you a sense of what I consider to be a significant jump. I'm hoping you can weigh in on how significant a jump you feel P7/HP50 -> JH13 is. If by the P7/HP50 stage I am already at 90% of world class and going to something like the JH16 is just taking me from 90%-95%, I don't think I would bother. Frankly the cost of the JHs and a portable amp is a lot of money for me and because I can't audition them I'm not sure how far past the P7s go before you start hitting the point of diminishing returns. Plus I will primarily be playing 320kbps MP3s out of a portably amped iDevice so maybe even if the JHs are that much better than the P7s then my setup won't fully show the discrepancy.
 
I listen to everything, but my favourite type of music is probably rock.
 
The two things I hate in headphones are when the bass is so overpowering it feels like it is muddying up everything else, which is my experience of the beats, and when headphones sound tinny/metallic/distant (I'm not sure if my terminology is correct, but it's the type of effect that happens when you turn the 1K slider right up on the equalizer).
 
I read the instructions about posting in the help and requests forum but I thought that because this was essentially a question about the ceiling of portable headphone quality it would be appropriate to post it here. Apologies if not and I will understand if it is moved.
 
Thank you very much for anyone who chimes in. I really love this site and the addictive quality of pursuing all of this beautiful audio equipment.

 

Bump.

 

Not sure that your question can be answered in the way you would like.  The difficulty may be that you are comparing apples and oranges...full size over-ear and CIEM's.  You can certainly achieve excellent SQ by either route, and you have identified equipment of both types for which you will find ample endorsements on this site.  In the quest for perfect SQ, like many other journey's, there is a point of diminishing returns...you may spend many $$$'s to get that last small incremental improvement in SQ.  Many have found sufficient self control to step of the train when it has reached the station...sadly, I am not one of these.
 
In my opinion, since you are generally happy with the Senn HD280 full size headphone, you should consider the P7/Momentum/HP50 path.  Any of these should be an incremental improvement over the HD280's...how much only you can say.  My advice is this...if you have the funds, and you like the sound of P7's, and they meet your lifestyle needs, pull the trigger and don't look back.

 

Thanks very much for your response, zomby. I think you're right.