I’ve looked at the Phonitor X and couldn’t pull the trigger on that price tag. Everyone here seems to think highly of it, and it looks like its specs say it can put 3.7 watts into 120 ohms, which ought to be plenty for almost all of your headphones. I settled on a Schiit Lyr3 as plenty good enough for the headphones I have (except for the electrostats, for which I have a modified older STAX tube amp).
I’ve had amps that can do crossfeed, and honestly, it’s not a feature I would consider a deciding factor. It can be good or bad depending on the recording. Not sure I’d like it with hardcore punk - I like the precise placement of a minimalist band - even if they’re in a garage. Soundtracks? Possibly - I have pressed the 3D button on the iFi xDSD listening to a soundtrack.
What @HeadphoneNoob said about there not being an endgame - Yes there are some pairings of amp and headphone that are just better than others. But I’ve talked about “The 95% Solutions” (The link is a topic on this forum) which although an older thread, is well worth considering. The principle is that you can save a lot of money by learning to be happy with only 95% of what you want. That extra 5% is what makes your wallet and mind cry out in agony.