Jgrage,
You have a lot of choices at it all depends on how big you want to go and how much you want spend! Like MYx said you can go with 15", 16" or 17" wheels you just have to watch the offsets and the tire width to ensure you don't have rubbing on the rear wheel well.
7 x 15" +34 offset wheels with 190/50R15 tires should not rub
7.5J/16" +35 offset wheels with 195/45R16 tires should also fit without rubbing, depending on offset you may be able to use a 205/45R16 tire.
7.5J/17" +35 offset wheels with 205/40R17 tires should fit without rubbing if you want the big wheel look. I have seen a few fits with 18's but I don't know about rubbing issues with thoses sizes.
I hope this helps you guys out. MYx I think if you go to a 205/40R17 tire it should stop your rubbing even with 3 people in the back.
D