The RA800 is the best of the group..64 voice polyphony, lyric reads , Sequencer and chord sequencer...The RA30 is a small compact unit..same 24 voice polyphony as the RA95[same engine, and same styles]..but you can not add other styles that you can with the 95..
If you don't need the extra styles or want to play sequences..the RA30 is a nice size for add on to your Yamaha organ..
I run across RA800 once in a while..they still bring $500..RA30's can be found under $100..RA90 and 95 under $200..