I have an Ultra 150 and I do not have to pre mix anything. My Ultra 150 is yet to be beat by anything. Yes there are jet ski's that will beat it but not to many. If you find one in good condition, get it. I have never had a single problem with mine and 2 strokes are way easier to work on than 4 strokes. Parts are cheaper too. The boat is also going to be much lighter. I was looking at a new Ultra 260X a few weeks back and while it is supercharged, and is putting out an extra 100 horsepower or so, it is a lot heavier than my ski and from my understanding, it is also around the same speed. The new Ultra 260X is probably quicker off of the line though but if you are looking to buy used to beat your girlfriend, I would highly recommend an Ultra 150 that has been taken care of!