Hi Art,
I am the second owner of the amplifier so I can't definitively confirm the age of the amp, however, the serial number had 05 as the last two digits so I believe that it was updated in 2005. When I get home from work this evening, I'll post the whole serial number.
I was very keen to hear the sound differences between the EXR6 and the Ultra amps. Reviews tend to focus on night and day differences but my impression after hearing both is that the differences are very slight between these two amplifiers. The Ultra might have more controlled bass in the sense that there is better definition to the lower notes. The Ultra might also have a quieter background. Of course, I could be simply justifying my Ultra purchase too.

My wife saw the EXR6 amp on the floor after I had swapped it for the Ultra and she thought I was still listening to the EXR6 amp so there isn't an easily discernible difference without a concerted effort to pay attention to different aspects of the music.
Let me know if you have any other questions.
Cheers,
Tom