Hi Bruce, The T* designation just applies to the lens coating. Most lenses for Contax are T*. What you want to pay attention to is if the lens is MM or AE. MM are the most modern lens mount and enable Shutter Priority and Program modes.
I shoot myself with the AX, and while I find the Auto Focus spotty in low light, the rest of the feature set has been very solid for me. I was torn between the RX years ago and the AX. Contax was in business then and advised me to go with the AX, since it has a more advanced focus "finding" system than the RX. So while the AX moves the internal body to focus and the RX simply gives you a focus indication, they claimed that the sensor is more advanced in the AX. I was attracted to the RX because it seemed a bit more solid. I traded up from an Aria because of reliability issues. I played with the RX and I feel the focus indicator can be trusted. It's just that you have to manually focus it.
Hope this helps,
Alan