for wheels (they aren't rims) check out wheeldude.com or the classifieds on here or nasioc. Seats...well that depends on how much you want to spend. rallysportdirect.com has a decent selection as well as basically any of the subaru tuning shops. Don't buy replicas just to save a few bucks, they are dangerous.
Im running A-tech final speed gear R's in bronze. They are made by the same company that makes mb weapon wheels. Nothing too fancy and fairly cheap. Mine are 17x8 and only weigh somewhere between 17-19lbs (can't remember exactly). For the price I don't think they can be beat (I got mine used for very cheap). As for seats I have Sparco Milano 2's in black but may be trading for stock 04-05 seats at some point