I've seen the white GT in Geneva and it looked stunning in white and glacier silver, like the pics.
I personnally prefer the Hexagon, leather is more for GT with Luxury Line.
I've seen a Miniral Grey Sport Line at the dealership and was disapointed with this colour.
I would take the Hifi upgrade, it's sounds great. The HK is if you only expect the very very best form your stereo.