Hi Denis,
Hmmm. Interesting. I used to own a Roland RA800 module unit myself, and I'm glad I sold it (about 3 years ago). I found it extremely awkward (if not impossible) to view & access it's buttons & screen, especially when using it in tandem with a separate keyboard controller board. If you are an accordian player, the RA800 may be a great setup, but if you play a 61, 76 or 88 note keyboard, I'd highly recommend against an arranger module type unit. For arranger keyboard playing, all the arranger functions (start/stop, fills, pads, sound/style buttons) need to be situated right at your fingertips (above the keybed) and this is just not possible with an arranger module unit. Just my personal opinion. - Scott