I have owned a few portable amps, and enjoy messing around with them. With some iems, you can notice small improvements in sq, but in environments where I choose to use iems (walking around, gym, airplanes, waiting rooms, etc) rather than fullsize headphones, there's significant background noise, I'm usually engaged in another activity other than just listening, etc., and it's not worth it to me to carry around an amp for that little bit of extra sq I won't even be noticing. I sold all my portable amps, but do keep a pico amp/dac, that I use with my laptop and ipod, but mostly for the dac, and with my Grados, not my iems. I am interested in the Pico Slim, after trying it out at CanJam with my UE11s, but I know that I'm just wanting it, not needing it at all.
If you're planning on using your 530s with a portable device, based on my experience, I'd recommend spending your money on getting a portable player with as much storage as possible so you can have a full selection of lossless music. That's where you'll pick up the improvements. If you plan on using your 530s as a primary headphone, as some people do, you might want to invest in an amp, but I still think that should be secondary.