Well if you're looking for decent sounds and want the synth without the full workstation features.., here's your choices:

61 key models
-------------------------
-Roland Juno-D
-Roland GW-7 (though an arranger Roland has it listed under their synths)
-Korg X50
-Yamaha MM6 (Mini Mo)
-Yamaha S-03
-Alesis QS6.2


88 key models
-------------------------
-Casio Privias
-Roland's newest FP series
-Alesis QS8.2
-Yamaha S-08
-Kurzweil SP-76
-Kurzweil SP-88
-Kurzweil SP-88X

I'd be iffy on the M-Audio's... Too many problems associated with those units. Not very reliable IMO.