I have an RX. Used to have a 159mm. My only (current) Contax SLR lens is the 50mm/1.4 Planar.
I also have an EOS3 and a Nikon F80, after 'experimenting' with an F100 and F4.
I had been planning to sell the RX, as i have the F80 to serve as a small SLR. But, after taking the RX out of the closet last weekend, i was quickly reminded what a fantastic camera it is. It just feels/looks so good.... The mirror return and drive are incredibly smooth.... The 50/1.4 is probably the best 50mm lens i've ever owned, save the M-50 Summilux-ASPH. I haven't tried the 50/1.7, but as mentioned above, i've never liked the bokeh rendering in images i've seen from it.
I have recently been considering the Aria, as well. Just to get the size+weight factor down. If it's true that the Aria's viewfinder is even brighter than the RX's, well, that sounds mighty nice. I just wish this series had AF — that's probably the only reason why i like the F80 in this context.