[zxcjason]

I bought a AKG K271 MKII for primarily for my digital piano setup which uses my PC (knowing full well I'll probably need an amp later on):
 
Keyboard -> PC  -> Onboard lineout / headphone out -> K271
 
My use for the headphone is primarily for monitoring my own playing, some composition work, and some listening (classical, jazz and rock).
 
What I find with my current system:
 
1.  Small sound stage:  Exactly what I'm looking for, so I feel like playing in front of my piano.
 
2.  Details, precision:  I need to hear the imperfection of my playing or production, so i want the system to be pretty unforgiving.  What I find right now is that the sound is really detailed when the volume is high and when the music is loud to start with.  With rock and pop that's fine, but with classical where there could be really soft passage it doesn't work so well.  When the sound is soft, it just sounds flat.
 
3.  Headphone out:  This is thru the motherboard header and connect to my PC case, probably not the best to start with.  The biggest I found is that with the headphone out, the base has much more life in it, as compared to line out.  However, the sound is a little bit less detailed. With piano and classical I like using the line out better, but the headphone out with rock and pop.  Headphone out also has inteference noise (probably from the computer)
 
4.  Colour:  I want the system to be as balanced, neutral and as little colouring as possible for production purpose.  I'm generally happy with the current setup but find the bass is slightly weak.
 
I have done some research and come up with some alternatives:
 
1.  ASUS Xonar Essence ST ($220): My preference as I won't need a DAC later on, and have the option of changing the opamp, but I'm not sure if it works well with my K271 because of its low impedance, and not sure about the balance of its headphone out.
 
2.  MEIER Corda Headfive ($190): Saw one on craigslist and some people reported good things about it.
 
3.  Other amp suggested in the forum: Heed CanAmp,  Pimeta, Gilmore lite
 
What would you suggest for my system and usage?  I also have the option of returning the K271 and get another pair of headphone too.  Any suggestion?

 

[SanJoseCanJunkie]

 
First thing - you don't mention a budget.
 
That being said, you've picked an excellent closed headphone for what you want; I think it's most important for you that you get an amp/DAC combo, and not just an amp.  Unfortunately, I don't have a great deal of experience with amps, although I will say that the 271 works great with the Micro Stack, and works less well with the EF2 and any portable amp I have tried.

 

[zxcjason]

Thanks for the suggestion.  I'm looking at < $250.  What I was thinking is to get an amp first and get a DAC/sound card later.  I agree that DAC + amp probably makes more sense for me (that's why I was looking at the xonar essence).
 
Another requirement for the DAC is ASIO, which I need for piano playing.