The set up that I am currently running is;
Head unit - Sony XAV64BT -
http://www.onlinecaraudio.co.nz/SONY_XAV64BT - this is a double-din touch screen unit with all the bells and whistles that fits in the original factory cage and the door still works. The one down side with this unit is that it does not control the aerial so an extra switch is required if you want to listen to the radio.
Doors and tweets - Focal 165 A1 SG component speakers -
http://www.focal-america.com/category/speakers/ - extremely crisp and clear full range and fit into the stock positions with no problems.
Rear Speakers - Digital Design DD-CXS 6x9 -
http://www.ddaudio.co.nz/cxs6x9.html - these fit into the shelf under the original covers with no problems or modification and have an extremely strong bottom end.
This combination of "European" sound in the front and "American" sound from the rear has produced an extremely full and rich soundscape in the SVX (loud too), the next step is to add a sub and I will probably go with an 8 to 10" Digital Design unit as they produce an amazing amount of 'punch' for their size.