there is a user on here to does a great number of recordings on a regular basis and he has some nice equipment. i would try sending a 'pm' personal message to "Rachfan" super nice guy, you can search users in the PM menu or just look for an old post of his in the audition room and click his name then click send message. in addition ot any info gyou get on here he would be a great source to seek out. also i only seem him pop into the audition board so i dont' know that he'll see this.
side note, i am SOOOOO incredibly jelous. the shigeru kawai is an absolute DREAM instrument. it is most definately on my 'if i ever have the chance to buy xxx piano, i will". i think you are doing the right thing looking for a way to increase the quality of the recordings and you instrument is capable of such beautiful sounds, colors, etc.
what sk model is it? are you in the US (the US market ones get the master artisan tech from kawai to come to your home to fine tune, regulate, etc the instrument if you purchased new rigth? i dont think the international market instruments get that).