Quote:
Originally Posted by
Nanago 
Contemplating getting these or their brother, the 600, but would you mind weighing in on what's most cost effective?
Now:
Motherboard -> Audio-gd Sparrow A -> K550
Possible:
Motherboard -> Audio-gd Sparrow A -> HD650 (500)
Motherboard -> Matrix M-stage or Lovely Cube -> HD650 (500 + 300/200 - What I can get for a Sparrow on FS)
Motherboard -> HD650 (500 - What I can get for a Sparrow on FS)
I really like Classical and Pop, but the K550s are a bit behind on pop, while phenomenal with classical.
Why do you want an amplifier? You know that your motherboard produces inferior sound?
Don't be fooled by the "if it costs more, it's always better", "external audio hardware is necessarily an improvement over internal hardware because it's external", or the "HD 650 needs a mega-amp" mantras. None has any basis in fact.
I use my HD 650's, and DT 990's, with the Matrix M-Stage and the ODAC+O2. The M-Stage is a good-sounding amplifier and it's considerably more convenient to use (for me) than the ODAC+O2. However, I prefer the sound of the ODAC+O2 as it's quite neutral -- more so than the M-Stage. The side effect of neutral is that it will faithfully reproduce the bad qualities of bad recordings. I describe it as "ruthless." If neutral isn't what you want, a tube amp might be more to your liking.
Your listening preferences should be the determiner here.