[WoodyLuvr]

I have thoroughly and completely confused myself about headphone/amp impedance, power, and sensitivity.
 
What exactly would I be gaining by plugging my B&O H6; v.1 (30 ohms - 97 dB/mW) into a headphone amp (<2 ohm)... instead of directly into my Asus Xonar DX sound card's line out (2 Vrms - 100 ohms)?
 
 
Improved low end?  Overall better clarity?  Or only increased loudness/volume?  Respects.
 
*** UPDATE ***
 
To NOT Amp, that is the answer!
 
As per PurpleAngel I just installed the latest UNi Xonar drivers with an astoundingly awesome improvement in listening!  No need for an amp now as 22-25% on the volume is kicking my butt and the sound is dramatically improved and clearer.  My H6s and ears are happy now.   I can't believe the dramatic difference... clarity, impact, and the bass is more detailed and lower sounding... even the timbre is better!  Thank you PurpleAngel!

 

[PurpleAngel]

  I have thoroughly and completely confused myself about headphone/amp impedance, power, and sensitivity.
What exactly would I be gaining by plugging my B&O H6; v.1 (30 ohms - 97 dB/mW) into a headphone amp (<2 ohm)... instead of directly into my Asus Xonar DX sound card's line out (2 Vrms - 100 ohms)?
Improved low end?  Overall better clarity?  Or only increased loudness/volume?  Respects.

The Xonar DX with it's CS4398 DAC chip, makes a decent DAC, so can't see any reason for replacing it.
 
For best detail in audio, it's better to have the source (amplifier) driving the headphones to have 8 to 10 times less impedance then of the headphones that are plugged into the source.
So for 30-Ohm jeadphones (B&O H6) you would want the source (amplifier) to have an output impedance of around 3-Ohms or less.
The Xonar DX's headphone jack has an output impedance of 100-Ohms.
 
FiiO A3 ($60) would be a good headphone amplifier (>1-Ohm output impedance) to use with the Xonar DX.
Or for more cash, O2 (Objective 2) or Schiit Magni headphone amplifier.

 

[WoodyLuvr]

  The Xonar DX with it's CS4398 DAC chip, makes a decent DAC, so can't see any reason for replacing it.
 
For best detail in audio, it's better to have the source (amplifier) driving the headphones to have 8 to 10 times less impedance then of the headphones that are plugged into the source.
So for 30-Ohm jeadphones (B&O H6) you would want the source (amplifier) to have an output impedance of around 3-Ohms or less.
The Xonar DX's headphone jack has an output impedance of 100-Ohms.
 
FiiO A3 ($60) would be a good headphone amplifier (>1-Ohm output impedance) to use with the Xonar DX.
Or for more cash, O2 (Objective 2) or Schiit Magni headphone amplifier.

Quick question... am I correct to believe that the FiiO A3 could be charged via my PC USB 3.0 Port (DC5V; 900 mA) as I have seen varying power input requirement specifications ranging from DC5V; 500 mA to DC5V; 1 A?

 

[PurpleAngel]

  Quick question... am I correct to believe that the FiiO A3 could be charged via my PC USB 3.0 Port (DC5V; 900 mA) as I have seen varying power input requirement specifications ranging from DC5V; 500 mA to DC5V; 1 A?

I would guess just about any USB port can charge the FiiO A3.