If your looking I'd give the Zephyr (caution TE wear), Ocius or even a Nighthawk a look, all are a step up.
I haven't flown the Ocius yet but I wouldn't call the others a step up from the SF ULs. The Nighthawk is a blast but it's small and fast. It's tough and makes a good starter trick kite if you get a deal on one. The Nighthawk was my 1st slack line kite. Many tricks are super easy but the Silver Foxes will give you more time to see and hit the tricks.
The Zeph can do a lot but it's heavy on the lines if the wind picks up even a little bit and around 10 or so it's pulling hard. Probably the best Prism for modern tricks though.
As far as the SF 2.5 / 2.3, the 2.5 are slower and maybe a little floatier than the 2.3 but still will hit most tricks well. Flic Flacs, cascades, Slots, 540 are all nice. I don't remember much in the way of oversteer on any of the SFs I've flown.