Well, if you need a good keyboard with good piano and organ sounds check out Alesis QS6, QS7 and a weighted action QS8.
They go for about $400 - $600 used.

Also check out Yamaha EX7 (not DX7 ) and Roland XP50.
All of those synths have nice on-board Samples and FX, so if you want that "Deep purple"Hammond C3 (or B3) or a clean rich grand piano sound - you got it.
I especially like the pianos and organs on the Alesis Q synths - very realistic.

-ED-