A preamp on a 500 series is recommended. With the 500 drivers, you should probably also get a DAC. FIIO makes great portable DAC+preamp devices. I used a Q1 on the go until it turned into dust. If you want to skip the DAC, though, you can get some portable preamps that work nice for a solid bargain.
@DA70D6 I originally intended to use them with a phone, so.... I'm now eying a combo from Schiit, because it's cheap but good, however Schiit Europe is out of stock.