mate, that would look stoopid with the 8's on the front and 6 on the rear! if you wanted the super fat look you should have got all 4 as 8 inch width.
195 is the tyre width in mm.
195/45/16's aren't going to look very stretched on 6 inch rims. 195/40's would look better. 215/35/16's could be good on 8 inch rims.
Style Dynamix are the usual suspects to talk about this kind of thing