Hi there, my name is Andre and I'm fairly new to quality headphones. about 8 years ago I got a pair of technics RP-F350 headphones that served me well until last week, when they finaly died. since their demise I have decided to buy a new pair of headphones and wanted something good but without breaking the bank. after reading for a few days I pulled the trigger on a pair of audio technica ATH-M50 because I wanted closed headphones for under 150 bucks and they seemed like the best option I had. Since I live in Brazil and I bought them in the US it'll be a week or two until they reach me. That being said I would like to know what else do I need to fully enjoy these phones. Up until last week I didn't even know amps and dacs existed and am still a little bit confused about when a dac is needed and when it isn't. I listen to music on the go using my samsung galaxy S3 and at home either on the computer(using the onboard headphone jack which I now know is a mistake) or through a onkyo A/V reciever. The questions I haven't been able to answer myself are the following: A) should I get a portable amp in order to enjoy these headphones using my galaxy S3? and if so, do I need a DAC as well? and last but not least, should I use the 3.5mm out on the S3 or should I get a USB line out dock? B) what should I buy in order to get a good sound out of the ATH-M50 when using them on the computer? since this is my first step into this world I wouldn't like it to cost me too much, so if you could keep the reccomendations to a low budget I'd be glad. last but not least, in the near future I'll be getting a pair of open headphones to use at home. I've been thinking about getting a pair of grado SR60i/80i to listen mostly to rock and alternative since they seem to do that very well and are very cheap. so I need the amp/dac that I'll be using at home to work well with these grados too. thanks in advance, Andre.