post #16 of 16
The reason why one would buy HD595s would be so they don't need dedicated headphone amplification. Decent amplification generally costs more than most phones, so the price/performance aspect of the HD595s is lost. If you're going to buy an amp anyways, you can step up to higher quality phones that may be harder to drive.

Edit:
I should add that I would personally never consider simply an amp upgrade w/o a source upgrade. It's either quality amp+source or nothing.