Mmike84,
If the Cary you auditioned "a few years ago" had SACD capabilities, it was not the 306/200. You must have had the CD 306 SACD, the predecessor to the current SACD Pro.
Regarding the difference between 303/300 and 306/200, I have heard both several times and just sold my 306/200 for the CD 306 SACD. I have heard the 303/300 in a setup very similar to mine (same speakers, tube pre). I don't think there is any significant difference between the two sonically. Something to consider is that the 306/200 has digital inputs so that it can be used as a DAC, while the 303/300 does not.