[jarbro]

I just made the jump from an HTC Windows Phone HD7 to the 4s and ever since all my tunes sound extremely flat and muffled.  The HD7 has Dolby Mobile and SRS processing for which gave it a great "3D" sound stage.  So far I am underwhelmed by the output of the 4s.  
 
I have been using my MEElec M6s and M9s, and even my Sony MDR-7506 cans which still sound flat.  So far the IEMs which give the brightest sound are the stock Apple earbuds, but they keep falling out of my ears. Being that I am a bit of a treble head, can anyone recommend a pair of IEM in the $75-100 range.
 
Note* All of my tracks are encoded Lame VBR 192-320kbps or Apple AAC lossless.

 

[NA Blur]

It sounds like an impedance problem to me.  Perhaps the output impedance is not matched well with your tests phones.  Try using a higher impedance headphone.  Try something at or above 100 Ohms and get back to us.
 
The next thing that comes to mind is either an EQ setting or volume limit preset on the phone.  Dig around in the sound settings and see if you can find those and adjust them accordingly.
 
Lastly be sure to try your IEM / headphones in another device preferably another portable phone or iPod.  This will ensure that it is not the headphones.
 
If it is possible on your network and budget try returning the phone for another one.  I suggest an iPhone because the DAC is designed for music and the output stage, at least one the touch, is pretty good.
 
Report back with what you find.

 

[jarbro]

I keep the iPhone EQ either off or on Flat. The Equalizer app definitely helps brighten things up.  I have tested my 4s vs friends with the same audio source and it is about the same. So it isnt my phone or IEMs.  I think I just need to find a better pair of phones.

 

[NA Blur]

Try listening to something by Tantric on your phone.  I use them for testing basic setups because they should sound up-front, very clear, the bass impactful and not out of place, while the mids to highs remain balanced.
 
Another test band I use is The Bare Naked Ladies.  They typically have had really good production and give some serious dynamics in their music.
 
Give those two a try with your 4s and headphones and let us know how they sound.
 
To be honest all of the IEM and headphones you listed are known to be pretty flat sounding.  You may be on the right track by realizing that your tastes may be for a less flat frequency response IEM / headphone.

 

[jarbro]

After reading the dsNuts review of the ATH-CKM50, I figure I will give those a shot before I invest any more.  dsNuts should go work for Audio Technica.
 
Amazon is great on returns so, I can always return them and get something else.