I would say at least a foot to the right, enough space for scissors, a package or pin cushion of pins, and stuff like that. Your 21-34" should be great. As long as you have the drawers underneath, that should be enough storage for you. I have a set of drawers that were designed to hold stuff like letterhead and carbon paper, so they're the size of a sheet of paper and a little more than 1" deep. I use them to hold buttons, zippers, transfer paper, bobbins.
So, I would use one of the cabinets, and overhang by an inch or so. You want more space to the left of the sewing machine, to hold the weight of the quilts you're making.