I would stick with what you have. A plus bike is a bit easier to control and has more grip, but the reality is that they are wildly inefficient and heavy, especially if you are going to take the bike anywhere near a road. According to the Bicycle Blue Book, you can sell that bike for 2800 tops assuming it is in perfect condition, and for that price you’ll be hard pressed to find anything near as good. Even if you did, I think you’d end up wishing for the Genius back.