I think the Santis' are the same width, 225 I believe.
I personally would stick with 16mm on the rear but you could maybe go a little bigger with no adverse affect.
On the front's I think you would really feel 15's through the steering. I went with 13 and it took a few weeks to get comfortable with the extra drag on the steering.
As regards brands, I bought Sparco and think they are brilliant and very affordable considering their quality.