Which in the $500 and under range that. can accurately cover different fQ spectrum

Hello,

      I was wondering that after purchacing a pair of Sennheiser Momentum Wireless over the ear 2.0, Because for my tastes now after having them for a cpl of weeks,cannot extend in the lower octaves with gravity as do the Dr Dre's Studio Pro's,and be able to play louder without total breakup! Well now im contemplating on getting a great portable lossless hi rez media player(e.g Fiio X5 or Cayin N3).From what ive been reading lately is that these players can far exceed the sonic perfomances our cellphones can produce!
And that maybe I can get a bit more bass extention,detail and better soundstage maybe off these cans! Orrr, get a second pair for use at home coupled with a decent headphone amp/dac!.And just use my Momentums for traveling purposes only in BT mode via a great entry level player like the Fiio X1 2nd gen.
If their is anyone who can possibly shed some light on my existing dillema,It would be much appreciated..