In reply to flopsicle:
IMO you do need to try on. Don't know any substitute if your feet generally have fit "problem".
Street size for me if the fit is right. Never got any Scarpa model to fit for me over the years - despite finding their walking boots excellent - but have found 5.10 the best fit, though others sometimes are ok. Just a personal fit thing; I find insole shape and how the lacing is to be very important for my feet.
Also, if your not intending to use for actual scrambling or climbing, don't go for the really narrow, tight fit ones. I regretted that - the few minutes of advantage can not off set the hours of why am I wearing these feeling! My 5.10s I mainly use are a bit generous which is great for most use, for casual use, approach to crags, easy scrambling, but can be tightened down by lacing when you want them to work hard on rock. Best of both albeit with a bit of comprise.