Cubase 4 has power panning, and its available in the project setup menu, under stereo pan law.
This is just my opinion, but i think its beneficial to use a plug in for panning, like waves Imager.
If you set the send to post fader, than panning in cubase will actualy occour after the sends, meaning that your send signal will not be panned, only the direct signal.
if you, however...use a plug in in the 1-6th insert slots, the signal getting fed into the send reverb WILL be panned, creating a clearer sound and a more defined spacial position, at least to my ears.
When its set to post fader, the send level controls the amount of signal getting sendt to the reverb, and the channel fader controls the dry\direct signal. So setting the right levels for thesee are integral for getting the right amount of wetness, and greatly varies depending on the instrument, and the placement in the virtual room. You just have mess around untill it sounds right.