I am thinking of buying a saab The factory deck is extremely expensive to take out so i was thinking of just leaving the factory in and putting in 2 jl w3's 12".
I heard that the nicer cars like saab bmw infiniti lexus all have high end systems anyways so the head unit doesn't sound much worse than an aftermarket.
These days, factory installed head units rival the aftermarket ones. It depends really. In Asia, Nissans used to go for Alpines. The higher end BMWs uses Harman Kardon. I'm not sure about Infinity (US) or Lexus. Factory installed systems usually blends with the interior of the car. It's usually the higher end cars that gets the better systems. Then again I have heard of a Nissan Altima with factory installed Bose in another forum.
Best would be to just stick with your current system unless you feel that it doesn't sound so good. I don't think car manufacturers such as Saab would go for a cheap sound system. You may probably need an amp though. Don't usually know of cars with factory installed amps!