I have seen posts here where people put a generous dollop of ready-made caramel, you know, that is made for dipping apples, into their buttercream. I tried a bit of caramel from Walmart, it is nice and thick, and whipped some in a buttercream recipe. It was really good. I tried once using ice-cream topping, and that was just too runny and lacked the flavor.
Love the SPS system....See Leah's tagline for instructions.