I just love the sound of them

 

620 is a good choice for an awesome looking first bike. On the buell the hp is 600 level or lower but the torque is much higher and when combined with a short wheelbase will make for a twitchy bike that you have to be somewhat smooth on. While you can keep the rpms low on a 600 and have a very docile and easy to ride motor you can't do it with the buell as it will have a lot of torque at all rpms. If its your first bike then buy one of the dozens of newbie friendly used bikes that are for sale around now......ride it the rest of the year and sell it in the spring for $100-300 less than you paid for it and get something bigger or newer. I've seen a ton of newbie friendly bikes for $1500-2200 lately which can be resold for the same amount