Hi guys,
 
This is my first entry in Head Fi. Would call my self an amateur Audio Lover not Audiophile.
 
I have the Sennheiser HD 457 for around 2 Years and Want to move to something better now.
 
First of all, I like Open style of headphones . I hardly need isolation as I will use them with my laptop at home and Also, comfort is an important factor as virtually My headphones are on my head 12 Hours a day .I don't care about leakage and my priority is good quality music , more over I live alone so Who the hell cares about leakage.
 
Further, My budget is 200 US$. I am not a bass lover but having said that, I do prefer a good and tight bass response but not overwhelming bass.  I like my vocals and mids to be strong and not too bright.
 
For my music taste, I listen to a lot of Rock, Metal,some dance/trance, Rap and ..that would be all. I don't listen to Jazz/Classic/Acoustic/Pop.
 
I have chosen 2 headphones on my own research, 1) Sennheiser HD 518, 2) Audio Technica ATH M50
 
I have two options,
1) As i will use a laptop as my source with inbuild sound card,I want to get a dedicated amp. So, I can go for HD 518 + Fiio E10/E7., this will sum up to around 200 USD
 
2) I can also go for ATH M50 + Fiio E10/E7 as well.
 
Now firstly, I want to know that are HD 518 a good open headphones for my style, and secondly, do they benifit from the use of Fiio E7/10. The same for ATH M50 as well and how much of a difference could i possible notice in both these headphones with amps. I have heard that the HD518 respond better to amp. as compared to ATH M50. How far is that true?
 
 
Further, a bit different topic, I want to know what is the difference between AMP and DAC. For example, E10/7 are amp dac, I understand the function of amplifier but what does a DAC do and how could it possible give better quality considering I use a laptop as source,.
Thanks all for reading and responding.

Audio is stored in a digital format (zero & ones), amplifiers and our ears are analog (wave).
So the DAC (Digital to Analog Converter) changes the digital audio to analog audio, then the analog (wave) audio is sent to the amplifier.
Computers (laptops) come with low cost cheap DACs, usually you can get a better external add-on DAC.
I say get the Sennheiser HD558 and the Fiio E10 USB/DAC/Headphone amplifier.
The Senn HD558s should improve more then the HD518s will using the E10.
The laptop send your digital audio through the USB ports on your laptop to the USB ports on the E10, where the DAC & amp. on the E10 do their thing.