Upgrade - sidegrade.. headphones set

[JediMa70]

Hello guys there are few months now that I've stopped to buy items and I just made an intense music shopping.
I've these 3 headphones:
Fidelio X2
Sennheiser HD600
Hifiman HE400I
(Darkvoice and Meier corda Jazz amps)
I'm wondering if I should replace one of them or to add another with a different "sound", maybe a closed one or so.. I'm still such a newbie so please be patient

thank you

 

[cossix]

If you want to replace the 600, the LCD2 is a good pick. A bit more bass but has much more detail and still has lively treble without getting annoying. I consider it a straight upgrade to the 650 so I think you'd enjoy it! Just bear in mind it is very heavy and may be uncomfortable

 

[buke9]

Depends on what you want different and how much you want to spend.

 

[JediMa70]

Depends on what you want different and how much you want to spend.

Well hard to say being not so expert, let's say that none of them is "amazing" for my favourite music that's hard rock and metal, or that none of them is really bassy (so they are already 2 options and that's why I was wondering about closed ones)
Budget around 200/300 usd but flexible on both the directions :/