My Dame Edna Aero has done over 120,000 miles. It has had the 300hp Hirsch upgrade since 19,000 miles. I have had virtually no problems with it. There are some cost cutting measures, but nothing that cannot be overcome.
Go for an Aero with the Aero Luxury Pack. This adds Memory Driver's seat and electric passenger seat, heated rear seat, heated front seats (maybe standard!), rain sensing wipers and the 8/9 speaker audio system. Without the pack, it's a bit bare.
Don't look for one with a satnav. The satnav and maps are as old as the car! And the unit was not good to start with!
My wife and I have driven the car all over Europe since we bought it in 2007. Buda pest, Verona, Venics, Pyrenees, Cartagena. Gibraltar, etc. It has been fine. Comfortable and good. But we also have the Hirsch suspension and brakes. 600 plus miles in a day is easy.
This weekend I drove to the Saab National and back on Saturday and To Leicester and back on Sunday. I'm really quite old now and I did it with no problem, despite spending all day in a fielsdin the sun at both destinations.
At the price they are these days, the Aero is the only one to go for. Any 9-5 Aero from 2004 onwards will be similar, that was the year that the engine was modified to remove the sludge risk.
I would question why you want a manual. I thought that I would never drive an auto again, but the Saab 9-5 auto is very good. I think that it accelerates so quickly that waiting to de-clutch for gear changes slows it down…
I would happily go for another 9-5 Aero auto estate. Mine even has ventilated seats for the hot days!!