Hello everyone. I am currently using the Sennheiser HD559 and Fiio K1 and am pleased with the sound. I would like to know if it is worth buying iFi Audio Nano iDSD LE for these headphones. I'm really interested in whether the quality of the sound will be noticeable since the price of these headphones is in the 100 Euro zone. Someone said that you do not have to spend on the amp / dac more than you have on your headphones. So, I'm interested if it's worth the investment. Thank you!