I would sell the YBR for as much as you can get for it and then buy something like the divvy for about half the proceeds of the YBR sale. People are saying that after a while you will want something bigger, but we are not all the same, and going from a 125 to a 600 is quite a jump, even with the DAS under your belt. It may be that you are quite happy to stay with it for a while, while you save up for your dream bike. (Although if your kids are anything like mine, that might take some time....).
