The good thing about all these choices is that you can just look for the amp that suits better your lifestyle.
Since you decided to go for JH16, which are supposed to have an emphasis on the bass, but will be using a source that is not supposed to emphasize it, it could be expected that you'll end with a somehow neutral sound. So in terms of sound signature, you could go with the RSA sound if you're more into dark sound, as they're reported to sound like that. If you prefer to keep a neutral sound, then you'll look elsewhere.
If you want to go balanced, then you reduce the choice to three models (RSA Protector, SR71B, iBasso PB2). The budget would likely be the decisive factor then, especially given the price of recabling.
If you're tight on budget, the Stepdance is reported to be a very good deal, while not lasting long on batteries. The Arrow is supposed to be another good deal and more portable, but not in the same class in terms of sound.
The Pico slim (Disclaimer : it's the only one I own) is by far the most portable of all of them, but probably won't be able to power big cans if you decided to go that way later on. It's also more expensive than some of the others.
The ALO RX, as stated above, could be a good contender but is rather on the high side for the price.
Anyway, you're the only one that can decide for yourself, according to your desiderata and needs. I merely tried to point you in the right direction, and I hope you'll find the right one with the first trial. Good luck !