ditto and ditto. earlier xp boards mentioned have lots of sounds, they go MIDI, and you will smile at the price. BUT that is to not exclude the FM sythesis group which might be a little different, but if you got one with enough presets, you would be successful in editing to get the sounds you want too. A D50 these days is CHEAP! I still have one that I use once in a while. "those great 70's 80's sounds" there's quite a stretch of 80's having FM Sythesis keyboards.
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PS Welcome, and thank you for not just asking "What's the best keyboard?". You see, we get that a lot, and -tek, a key member sometimes gets upset and unloads on the poor guy LOL.