Don't be tempted by cheap prices at Performance!
I find that there stuff - while generally running "true to size" - tends to be ill-fitting and uncomfortable. I have a pair of their knickers and they feel like they're constantly falling down (just say NO to crack!) and they just don't fit right on my hips. I think the fabric wears out before the chamois, which is fair, and they're passable for short rides at best.
I've sworn off Performance brand, but I can't speak for Nashbar or Adidas.