Bingo! Thank you so much... not perfect, but good enough to get me working again. Have not tested all sources, but briefly:
RX 630 - no good, printer scrolls blank pages, had to interrupt...
RX 640 - works well, some colour problems (blues come out as pinks but only on actual printer output, pdfs/scans stored true to colour, although I guess the scan driver is separate?) but otherwise seems good;
RX 680 - same as 640 but takes 10 times longer to print each page...
A few residual problems such as Safari quitting mid-print/pdf from some website specific print commands but certainly no worse than prior to 10.6.8 install...
I was figuring on sticking with the RX640 driver until and unless the OSX upgrade fixes it - any other advice?
Thanks so much for this