For me, thread weight is more important than brand (although I really like presencia for piecing). I use a 60 wt for piecing and, depending on the look I'm going for, 40 to 80 wt for quilting. I use cotton for piecing, and cotton, poly or a blend for quilting.
As far as fabric, I have found great fabric for $2 at a chain store and have seen really bad fabric by name brand manufacturers at specialty stores. I like to touch it first to estimate it's quality.