Hi everyone I'm new here (and a bit of a noob when it comes to audio equipment) and this will be my first post so I apologize ahead of time if my questions seem obvious, nonsensical, or even stupid. I've recently ordered a pair of Sennheiser hd 598s that should be here shortly and have been wondering what type of amp/dac I should buy. I'm not exactly sure what an amp/dac does (if anyone has an explanation in layman's terms it would be very much appreciated) but have heard it will greatly improve my listening experience by increasing sound volume and driving the headphones. I've come across the Fiio e17s but I don't know if there is a better alternative for the price or if it may be over kill. Also I would like to know if will I need to purchase a part to hook the amp/dac to my iPod such as a line out dock (If so I wouldn't mind a recommendation on this either) or if those parts will come with an amp/dac. My budget for and amp/dac is up to $150 but I would prefer not to spend this much but I am quite willing to pay over $100. My other question seem quite silly since I've already ordered the head phones but I can return them if need be since i have not received them yet. Did I make the right choice in headphones? Unfortunately I live in a city where I have no opportunities to try on quality headphones and hear how they would sound so I was forced to research online for a good pair. Eventually I decided on the hd 598s. I read they are good quality headphones its just I've gotten buyer's jitters as these are the first pair of really good (at least I hope) headphones I will own and it is a large purchase for someone like me. I listen to a lot of jazz, classical, electronic (not really house music more in the style of Kraftwerk though I do enjoy Italian disco),soul/R&B, folk/country, bossa nova, and pop and someone who does not enjoy too much bass just the right amount so I feel I fit the description of someone who the hd598s are geared towards. Will they sound better than my Koss porta pros? I wouldn't mind some opinions on this either. Sorry about asking so many questions.