For cheaper shorts, I think the Sugoi is wonderful. At the upper end, I think the Assos F.I. Mille half short are pretty awesome, and they come up to XXXL, though they use funny names (XL, XLG, TIR instead of XL, XXL, XXXL). I've heard great things about Giordana, but haven't worn. The Assos is wonderful even after 70-100 miles, no complaints at all (though I ride with bibs instead of shorts on longer rides, it's the same chamois).
Someone will chime in with the appropriate Performance or Nashbar shorts for truly budget shorts, but I have no experience with them and am not comfortable guessing which is the right one.