If you want a sound like a korg polysix try the Alesis Micron . Its a little digital synthesizer but it have a very cool vintage sounds and it’s low cost .
But nothing beats analog .
i don’t know how “new” you want. but, an ensoniq esq1 or sq80 could be had for around 200 and has a nice old sound. they both have 61 keys and the sq80 even has aftertouch. it’s late 80s which is new to me…
There are many good keyboards which provide excellent results but you should first decide your budget before buying any.
If you want high-range keyboard then go for:Yamaha Tyros 3 Professional Keyboard($5,499.00) or similar ones.
Entry level:Yamaha PSRE-323 Portable Keyboard With Survival Kit($269.00) or similar ones.