I've owned both ARC (SP-15) and Sonic Frontiers (Anthem Pre-1) preamps, and the CAT SL-1 III (with phono) that I'm selling on Audiogon is worlds better than either. Not to make an ad out of this comment, I agree that you should go by your own ears, if you're determined to get either ARC or Sonic Frontiers. But there are a lot of much better preamps available on the used market, like mine with its customized signal path. Good luck with your choice.
