Sean and Gregm, in my experience PRaT can also be enhanced by slightly raising the midrange/midbass output. I have also a weird experience that after I inserted my very simple DIY unshielded S/PDIF digital interlink (that has an impedance that is far from the specified 75 Ohms I guess), there seems to be more PRaT and midrange fullness. I'm starting to believe that jitter also can improve PRaT (which is actually a contradictio in terminis)!
Chris
Chris