There a lot of excellent ways to drive the Focal Clear. They’re not particularly demanding power-wise (even the DragonFly Red and Cobalt can drive them to instant-hearing-damage levels) , scale well and don’t have any tonal or behavioral weirdness that needs special considerations.
While the Clear can certainly exploit the full capabilities of the Phonitor X and XE, if you’re not going to use their additional functions they’re probably overkill - and you certainly don’t need nearly the power they can deliver.
The DAC192 module for the Phonitor X isn’t terrible, but you can do better externally for as little as $100-$150. However, the amp and the Clear both deserve more. The DAC768 module for the Phonitor XE is supposed to be a lot more capable, but I haven’t heard it (and it’s also a ~$700 option). But if you want an amp you won’t have to think about in the future, the Phonitor X and XE are definite, and strong, candidates. And there’s an XE with the DAC 768 model as open-box/used available from headphones.com for $2,299 I believe.
Taking a step back …
You’ll get excellent results out of something as simple as the Schiit Modi 3/Magni 3 combination, or the Grace SDAC/JDS Atom. The Topping DX3 Pro is very good if you want all-in-one capability as well. All of those will come in under $250, shipped.
They’re a pain to get, but a Grace SDAC Balanced/THX AAA 789 would be the next meaningful step up, at around $550. You could substitute any of a number of other DACs there, and the Topping DX7/D70 are viable here (the DX7 on it’s own is a lousy match for the Clear, even though it has a headphone output, since the output impedance is way too high and screws up the frequency response of the cans).
The “sweet spot” is probably either the RME ADI-2 DAC fs ($1,099) or the Holo Audio CYAN PCM ($1,299). The former has way more features, the latter I have a slight preference for the sound of (though the RME unit is definitely more accurate and offers higher fidelity).
The ADI-2 DAC fs has one weakness … a tendency towards slight dynamic compression from the amp. The highly-dynamic nature of Focal headphones tends to minimize the audibility of that, and most people can’t tell its there anyway (it’s really only noticeable in back-to-back comparisons using better amps), but if you went the RME route to start with, you could always add an amplifier later.
Solid options for an amp to pair with the RME are the THX AAA 789, Jotunheim, Lyr 3, Phonitor X/XE/E.
There are others, such as the other ~$500 THX-AAA units (Monoprice and SMSL), and the Schiit Bifrost 2 is getting excellent reviews (as a DAC alternative to the RME) but I’ve not heard those myself so won’t recommend them.
So that’s all well and good … but there’s a not-well-known option that you’d need to pair the RME ADI-2 DAC fs with the Phonitor X/XE ($3,598 total) to beat …
I will likely have the rest of my episodic review of that, focusing on sound/performance up either later today or early tomorrow (and we have a thread on it here).
Those run $2,499 new, though headphones.com has an open-box unit for $1,999 currently.
The Arche has demonstrated excellent synergy with all of the Focal headphones I’ve tried it with (which is, well, all of the Focal headphones …). Some aspects of it’s performance with Focal cans is preferable to my “review-reference” RME ADI-2 DAC fs/Phonitor X combination.
The DAC section doesn’t let the amp down. The amp doesn’t let the DAC down. And you can access both functions separately. It’s the best-balanced, and most enjoyable, all-in-one I’ve heard so far until you start getting up to things like the Chord Hugo TT 2.
And it’s not just good with Focal headphones … it’s been wonderful with everything I’ve tried it with.
It even has an analog input (just one) for other external sources (if you need more than one, passive input switches are inexpensive and won’t affect the sound). Though bear in mind that the Phonitor X and XE will also only have one available analog input left if you pair them with an external DAC.
If push came to shove, I’d personally either go for the RME ADI-2 DAC fs, enjoy it for a while, and then decide if I wanted an external amp (and if you did, and wound up waiting for a THX AAA 789, you’d still have the built-in amp in the mean time).
Or I’d just cut to the chase and get the Focal Arche and call it good.
That’s mostly a budget/features call.
Hope that helps!