I use both a Mackie and a Behringer mixer and think both are of excellent quality. I don't know why there is such a price gap, but both perform equally excellently. Right now I'm looking at adding the new Alesis USB8M mixer to add to my mini studio. It has 4 XLR channels, 8 in all. Full in/out with USB connectivity to computers and DSP FX ($149). It seems solid and the saleman at GC said he was impressed with it so far.

As for headphones, I prefer and use a couple different Sony MDRs.