Springs vs Valving

I have a 99 KTM 250 EXC with the static and race sag set to the manufactures recommendations. I would prefer the bike to be a bit more plush when trail riding. The rear of the bike seems to jump around a lot especially when riding it hard. I've tried adjusting the clickers on the forks and rear shock and they seem to only have a minimal effect. My question is should I try different springs or change the shock valving? When I took some of the preload out of the rear spring it seemed to ride better. Any suggestions would be greatly appreciated. Mike

I probably should have added to my original post that I weigh approx 200 lbs and I am a B rider. I ride mostly woods with an occasional Enduro or Hare Scramble. I don't Mx and the only jumping I do is over logs. (Its tough getting old!!!!!) Mike