Well why just don't you go for 24" wheels while you are at it. Kind give it that Conestoga Wagon look that so many folks crave, then with the low profile tires, and lowered suspension you will need to roll your fenders to accommodate the rubbing and shredding of your tires then complain about the rough ride.
Excuse the rant, as it would better serve you to take care of the Maintenance items on a "new to you" car than worry about rims/tires. I am not saying that you shouldn't upgrade, just as a new owner I would be taking care to inspect/replace, brakes, hoses, plugs, wires, and the like prior to
looking in to rims.
One of the Best places that you can vist for all your cabby questions are:
And if you haven't bought a Bentley Manual yet, let me say, you'll need one.