I'll just say this. The shortest time of any car I've ever owned was my Volvo S60R. The theory behind the car was fantastic - Turbo I5 300hp/300 lbs/ft AWD.
However, the reliability was mediocre and the dealer network was clueless. And believe me, I tried a few.
The S80 is a big car and I'm not sure how or why anyone would compare it to a 135 - no offense.