"avicenna" wrote in message
My question is this: would I need anything aside
from the mixer and a set of headphones to pull this off (eg., would I
need a power amp of some sort to boost the headphones' level)?

Short answer: No. The mixer amplifies the signal to headphone level.
That's why you have both line outs and headphone outs from things like
mixers, portable CD players, etc.