Hiya, I'll have a glass of red vino if you dont mind
My thoughts? (I dont have an S4R, tho I do have a M1000sie) is that I'd keep the 620 for the commute.
I really wouldnt use mine for the filtering work, without changing the clutch lever etc (which I am quite happy with for the rest of the time

). Its far too torquey (sp?) for the on/off throttle & slow speed stuff, and IF on occasions I've been stuck in heavy traffic etc, I am swearing like a trooper about getting a ssshh..... jap bike if I had to commute daily....
Ak's enjoyed the 620 tango for commuting recently, says he prefers it over his lawson (who wouldnt

) and better than the M900 special too
Get an S4R (if thats what rocks your boat) for the fun w/end stuff if its within the budget.
Happy shopping
C