I have found the Super Cardoid Neumann KMS 105 condenser mic - it will run you about $600 plus, but worth every penny.
I think that mic is awesome, but fails to overide the on board preamps of any built in keyboard I've ever had. I SO wanted to love it, but plugging it into my Korgs, Yamahas, Ketrons etc ... it never outshone the EV/Sennheiser class I have been using. When plugged directly into a better desk - It's amazing, but coming through a built in kb setup - you don't get the extra money's worth IMHO.