VXR8 Sat Nav and Power Upgrade?

[426Hemi]

I am looking to buy a used VXR8 in manual and have found that there are none with Sat Nav as a add on...it is possible to add the module box in?

Also I have seen a few with a 600 HP supercharger upgrade by Wortec...is it comfortable as an everyday car and how is fuel economy (I know its barely going to get 20 MPG on a standard one).

Thanks in advance

[hsv_rulz]

See this
www.hsv.org.uk/topic.asp?t=701582&f=69&h=27