Now I know I can't just buy a set of tires and rims and make them fit and I'm a bit of a n00b so what should I be looking for, for my stock 03 9-3 linear in terms of rims/tires, bolt patterns codes I need to look for when buying? Thanks!
After that it all boils down to wether you want performance or bling-bling. The more the tire/wheel combo weighs the more performance you lose since every pound is rotational weight hence it makes a big difference even though it seems like such a small amount.
The general rule is try to go wider profile tires for the summer and stick with the factory wheels for winter tires because wide tires in snow have a lot of trouble plowing all the extra snow that thinner tires will cut through.
Not true. It is true that suspension is tuned based upon the equiped wheels/tires, and the more radically you depart from that you may notice differences (i.e. a heavy, non-performance 19" bling wheel) in handling characteristics.
However, realize also that 18" wheels are an option/accessory in Europe (check the saab uk site).
Accordingly, handling may change, but it's unlikely to be "really bad"