Recommend a retune as well if you add intercooler and 17 ect.
The 17 will give slight gain at lower rpm but no gain at top as its spinning faster than the supercharger can handle.
I was in the same boat as you and still went for the 15,
But this is just my opinion!
There are load of thread out there on this topic, some people really do like it and then there's people that don't.