[Envyous]

I currently have a DT990 Pro 250ohm together with a Asus Xonar Essence STX on my PC. First question is, should I have an AMP/DAC/whatever for this setup for better sound?
 
I am also interested in using the same headphones on the go (iPhone currently) and, most imporantly (most of the time) at work (stationary PC with motherboard sound output only). What amps would be best for this?
 
I know "some" of the amps has DAC. Is it worth having? I guess you can't use the amps with DAC on a phone because they require an USB output?
 
I am most interested in FiiO amps because I hear they are affordable and great. You do not have to find one that fits all use cases, I am willing to buy more than 1 amp if it is required.

 

[pbui44]

There is the FiiO e12 (0db and 16db gain settings) as an amp and FiiO e17k Alpen 2 (0db, 6db, and 12db gain settings) as an amp and DAC. Both run around $130, give or take $10 or $20.