The cheapest options these days are for headunits that have links to a smartphone. These are listed as having Apple CarPlay, or the Android equivalent. That way you get a good radio, often DAB, and then you use the phone link to provide the satnav, music, etc.
I fitted a Pioneer SPH-DA230DAB in my 2007 9-5 and it’s working fine. You don’t need the GPS shark fin aerial any more as the phone has its own aerial. I removed mine and fitted a DAB aerial in its place.
Someone like
www.incartec.co.uk will do a loom, which makes it virtually plug and play. Not too difficult DIY, but any half competent audio place “should” be able to do it.
Many head units have line outputs as well as speaker outputs, and these work with the existing Saab amp, with ground loop isolators. Or you can use the speaker outlets with a voltage dropper. Otherwise the volume control could get very loud and break things.
