I also had an SX-K200.
I bought it in 1982 for £299
It was one of the very first proper accompaniment keyboards and was finished ( I think) in a nice silver and black.
It offered the usual styles of the time being 'swing' & 'latin' and 'rock' etc but only about 8 of them. similarly with the voices, standard 'piano' and 'guitar' and
'brass' and somrthing called 'cosmic' I think.
It also had a plug-in module to play prerecorded chord sequences for such songs as
'Roll out the barrel'
I was captivated by it and had it for several years before trading up to a Yamaha
FE organ.
A friend of mine still has has Sx-K200
A great instrument in it's day.

Petere