this is should be an easy ? for you guru's. .is it better to mixdown or bounce vocals before you mixdown all of your tracks or is it better to just mixdown all at once?

Is there a reasonably priced pair of headphones that could be used for mixdown without too much coloration? Or even a pair that isn't reasonably priced? I'm worried if I use speakers, that the sound of my room, or of the speakers will throw me off. For that matter, what is a decent pair of near field monitors going to cost?
Andy

Hey...

I'm using SONAR XL 2 and a MOTU 2048 mkii for my recording. I'm monitoring through a set of medium quality headphones. Typically, I record everything into SONAR and mix the tracks down to a WAV file.