The two seats in the back was to probably make it more comfortable for the people riding back there, I've had three other people in the car and we all seem to fit just fine. Also the Volvo 480 was sort of it's spiritual predecessors, which was a unique for the time 2+2 sports wagon thing.
The Polestar tune wasn't cheap by any means, I think the work order said $1,295 but with tax and labor charges I think it was $1,400. It's almost double what some of the other tunes for the car run but I figured Volvo themselves would have a better idea how to tune the car than some aftermarket tuning company. The Polestar tune also had the added benefit of still being covered under the factory warranty.