Thanks to Bros Promrakthai, Fong, Night Devil, Sexcuore, KLKool and Donzdonz for your replies and recommendations.
Really wanted to try the Spa de Palace as this seemed to be the on the 'best of' list but unfortunately my schedule was too tight. Settled for the in-house spa (Horizon Spa) on Sunday afternoon. Not too bad, $68 for normal, $188 for special.
Will try the Spa de Palace the next time I'm in KL again. Cheers.