I would suggest as follows

Sennheiser HD650......... £258
Focal Elear.........~£800......... Review

For IEM's, the Shure 215, 535 or 846 are the ones to go for IMHO and pair very well with the Explorer [and Prime]

Suggest you find somewhere to demo the Elear.......newish HP's but as can be seen from above and similar reviews, they really work........and have low impedence, so work well with the Explorer and Prime

The HD650's are a long proven classic that I've used for more than 10 years........punch WAY above their price.......and for most listening are on par with the HD800 IMHO [without tweaks]........the HD800S are better, but still not a match for the Elear's IMHO

Lastly, no substitute for a long term demo [at least 30-45 minutes.......days at home if possible]........to see what sounds good........but just as importantly what you find comfortable

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