Glad to hear you're enjoying GPO. You've just found a very help community of GPO enthusiasts.
If you could give us a little more of a description of what you mean by turning to mud we'll be much better able to assist. (Do you mean balance or general quality? Can you post a sound clip example?)
If you have all of the updates (the most recent is the August 2.2.3 release of KP2), then this is what you want to use to give you the best programming on the library. Juding from your previous use of the Wet patches, I suspect the mud problem lies in not having any reverb on the samples. The Wet patches use Kontakt's built-in reverb to give the otherwise dry samples some space.
Try adding a reverb effect in Kontakt Player 2 to improve the sound:
-Open the Output menu.
-Click on Show Inserts (or maybe it's effects?)
-You'll see four slots appear above each output. On the Primary Stereo out, select either Reverb or Convolution. You can tweak these (or import an impulse response) to hopefully improve the sound. One note about convolution: there may be a bug interfering with the drag and drop adding of an IR, which will require you to load the IR in KP2's standalone and save it as a preset there, which can then be loaded when KP2 is running as a VSTi.
Thanks for the reply. Let me just make sure I understand. When I load "GPO" into Cubase, the module that I load into the instrument rack is called Kontakt player (rather than Personal Orchestra, as it was previously).