BALANCED VS. UNBALANCED ON THE P1:
I've spent a lot of time with these in both modes and
I don't think it matters - they just need a ton of power, more power than any of my other iems. They sound unreal SE (unbalanced) on the iDSD Micro BL - with some EQ they have tons of bass. They also sound amazing balanced from the XCAN. But the XCAN balanced output is much better than its SE so of course I use a balanced cable with it. The iDSD is only SE, but an absolute power house.
Obviously sound wise, the iDSD Black Label single ended > XCAN 2.5 balanced. But it's not a perfect 1:1 as the Black Label has a ludicrous output of 4W to the XCAN's modest by comparison 1W.
So IMO when looking at amps for the P1, I would 100% take power over balanced output. I would say the minimum max output for an amp should be ~320mW. With 1W or more the ideal amount of power. I know there's a big debate on head-fi/reddit/everywhere as to whether balanced has any advantages over unbalanced in general, but I don't have an opinion on that.
But with the P1, I didn't think there is anything missing going from balanced to unbalanced.
P.S.
@Timoteew - the JDS Atom seems like a great fit (it would perfect if it had a hardware bass boost
).