I would definitely recommend an adjustable bar. You will end up only using one setting, but it's better to buy one bar with 2 settings you don't need than a stnadard bar with one size you don't need.
But, consider going without at first. I never felt the need for a front sway on my RS, but that was personal preference. If you want one sooner, go with the Whiteline (non-XRD) or Perrin, or Progress, or Cusco, or... well you get the idea. Same parameters as springs. Name brand, best deal you can find.