IMO, you don't need expensive bourbon to add to a beer. You can get cheaper bourbons with good flavor that will work just fine for your purposes here (and some are fine for sipping, too).
From your list, I would go with Four Roses (I assume yellow label) or Maker's.
Some of the less expensive ones you might consider would include Heaven Hill, Ancient Age, Old Weller, or Very Old Barton. I went on a budget bourbon tasting spree a year or so ago and these were some of the better ones. HH I'd probably reserve for mixers, but the other three do quite well on their own.
For the price of Woodford Reserve and Knob Creek, I'd pour it over a couple cubes rather than into a beer.