I have the MegaWorks (Cambridge's high-end before GigaWorks) and they're awesome. You can probably find them for $200 or less. Though since you're looking at Z-680s and ProMedia Ultras, I'm going to guess that you plan the spend more than $200. I've never listened to the Z-680s or Ultras, but my brother's ProMedia 4.1s are great (slightly better highs than MegaWorks, seems same otherwise).