I use a lot of different things. I use a real Fender Rhodes and Analog Synths whenever possible for those kind of sounds (Moog Little Phatty and Juno-60), and when recording use a lot of soft-synths (the arturia stuff is excellent).
For an all around kind of board (pianos, electric pianos, synths, strings, etc) in a decent price range, your best bet is probably a motif le. to my ear, their sounds are better than roland's and korg's in similar price ranges. if you're looking for a dedicated synth, at under $1000 you can get:
roland jp-8000 (only available used) $600-$800
Korg Ms-2000 ($300-$500)
an old Juno $300-400
the new roland GAIA looks pretty awesome too.
those are all pretty cool analog or analog modeling synths, and have tremendous capabilities and will teach you tons about creating sounds using osciltors and filters.
as for work stations, i've moved away from them since you can do so much more with such a better interface using a laptop and an inexpensive firewire or usb interface. you can use pretty much any new board as a midi controller, and a lot of the programs come with decent strings, piano and drum sounds right in them. for the same money you'd drop on a good workstation you can get the software, interface, and controller, and have some change left in your pocket.
If you want a board that does the vintage keys thing (e-pianos, organ, clavinet) nord makes a bunch of them at different price points, but to my ear, only the new ones really hit the sweet spot.
Hope this helps.
