For me its not the overkill, its the quality of music that ill be getting. In time I can say youll be upgrading your headphones to a higher level(i guess) and with a good source you can really hear the potential of the next upgrade you will be getting. Im sure this investmet will be worth it.
But one thing, audition it first before you buy.
The upgrades I foresee would be headphones that surpass the Momentums portability with quality. Since spend a lot of my time listening on the train and at work, I like to listen to my music without bothering others. As much as I would like to buy some higher level headphones, the reality for me is there's not enough large gaps of time for me to be at home and enjoy those headphones, so I've stuck to my Momentums.
Although money isn't a concern for me, I still like to buy things appropriately for my requirements. If it's still appropriate for what I'm doing with it I'll append it to my to-buy list .