I'm not positive, but I think the RS and the S are slightly different.
Same motor, but the RS has more body work, IIRC.
I only know what I know from reading a bunch of suzukicycles.org, or whatever that website is were a guy has gone through and cataloged every suzuki mc (ever?).
I bumped the DR650S thread (something like "Any DR650S owners?") Not a ton of info, but it's got some, and it'll help you find who has one and who knows something.