qp gts

I'm thinking about ordering spacers for my QP GTS. I have the OEM 21" wheels. What sizes do you guys suggest for the front and rear? I'm considering lowering the car so I want to make sure I get them closer to the outside of the fender without rubbing. Thanks for the feedback!

I am considering to buy a gts, with 12.000 miles, first immatriculation June'10. I am totally new on Maserati, and while I imagine the cost of maintenance is probably much lower than in 12 cilinder Ferrari from the 90's / early 2000', I am sure the cost will be higher than in a modern Merc' or...