Generally 88-note keyboards are either Stage Pianos (cheaper and lighter, but not many sounds) or Workstations (full of sounds but heavy and expensive).
The one that stands out as combining both is the Yamaha MOX8, which has lots of sounds and is very light for a 88 note keyboard (which will be (very) important when you gig with it). It's a synth, rather than a full-blown workstation and the keyboard is not to everyone's taste, so try it before you buy it.
PC3x is also a great choice if you can find one at a discount price. It's rather heavier than the MOX8, though, and they're now discontinued but there should be some left in stores.
