didnt know those 132 were available in 20"s!

I love the 20"s of the 4.6is as I have them on my X5!

You cannot have the set up 275/40+ 295/40 because you would be raising your rear end!Your wheel/tyre diametre would be 16mm more at the rear !
Some members here have 295/40/20 all round but they are also 16mm up oem rolling diametre!If you can ,go for the oem set up(275/40+315/35).
For winter,ii is advisable to go with a different wheel/tyre set up (eg.18"s)