I just checked my RX65 today and realized that it is version 3.2 not 3.6. Called up Bel about this and they told me that the difference between the two revisions was only small engineering differences. I'll call back some time and see if I can speak directly with a technician to get a little more into.
Also, I mentioned that I had heard rumors of a software update for the X50. The man that I talked to told me that there was no planned updates for either the RX65 or the X50 so far as he knew, but an update was planned for the regular 8500 to make it more comperable to the X50 within "a couple months".