Audio Technica I know these headphones have been highly reviewed and such, but I am still unsure which I should get. Main goal is to get the flattest, most natural sound. There is a frequency response chart for the M50, but I can't find a graph for the M40, so I have to go by reviews. http://graphs.headphone.com/graphCompare.php?graphType=0&graphID=1513&graphID=1473&graphID=533 Which appears flattest in the above chart? The M50 is said to be flat, but with a tad bit too much low end. The M40 is said to be flat, but some say the mid's are a bit high. I need the headphones to hear vocals. I think vocals are mainly crucial in the mid and high end so would the M50's be most accurate for hearing the most realistic vocals? I know I sort of answered my own question, but just looking for professional advice. Plus saving $60 getting the M40 over the M50 would be nice. But natural sound is more important. I can get the M40fs for $65 new over the M50 for $120 new. So just about double. But if the M50 is really worth it over the half-cost M40 I will get them. Can anyone graph the M40fs on frequency response? By the way, I am using a Focusrite Scarlette 2i2 USB interface. Will the built-in headphone amp be enough to use either? The M40fs is 60 ohms while the M50 is 32 ohms. Not sure how this works out yet. I don't know if or when headphones would require a seperate amp. So this is also a big decisive factor for me.