As to the particulars I have spent time with the RF 7's, 5's etc. and own Cornwalls but I think maybe we should rethink your question.
First there is room size. I suspect the 83's will work better in a smaller room, and Cornwalls do sound their best near a corner or wall and with a little room to breathe. Also the Reference line really is marketed (and probably voiced) as more of a HT speaker.with good WAF appeal.
Then you mention you're picking up a Mac tube amp.
Then there's a question of weather you are going to be churning your system or do you intend to hold onto the speakers for along time.
My own opinion, but if you have a nice size room, tube amplification, your not interesting in trading in for a new sound every year or two, and your primary concern is music, not movie, fidelity than the Cornwalls are the way to go and the extra money you spend will yield a commensurate sonic pleasure.
Cornie and tubes, yummie, RF's not so sure.
He was a legend in his own mind.