If you have never had the experience, a short ride on a properly setup Ultegra or Dura Ace Shimano setup OR a Campy Chorus or above setup will be a seductive experience. Once you try it, you WILL find someway to justify the expense, and if you really enjoy your riding, that is not a bad thing.
Modern Shimano DA, Campy Record, and SRAM Red are a little too rich for my blood, but Ultegra, and Athena/Chorus are nice sweet spots.
PS I have no experience with the SRAM road group, although I would like to try one. All reports are even the lowest level Rival shifts as well as the next up Force, and differs mainly in carbon fiber contact.