The thing that has always puzzled me about you Paul is why that someone who doesn't want to play music keeps buying synths ( You have mentioned on a few occasion that playing or creating music doesn't really interest you much. It would be like someone buying sets of golf clubs but never played golf ). Is it sound design you enjoy ? If so I'd say don't go for the expense of hardware when you really aren't going to use the keyboard. It would be much more inexpensive to experiment with soft synths plus you can try out demos of them all and not have buy them before deciding they aren't for you. Though even sound design only really shines when you hear the sounds used in the context of music or a sound FX track.

Before anyone can advise you on how you should proceed with choosing a synth we must know what it is you want or expect to do with it. Do you know the answer to that ???