I had this dilema whilst looking for my current car.
I really liked the look of the alfa 159 but the boot was smaller than the one on the vectra I was replacing.
current mondeo is nice but its a BIG car, way bigger than anything else I looked at.
Octavia looks dated and doesnt have much leg room in the back.
I would avoid the insignia as its a pile of crap.
I even looked at a 5 series bmw but they cost to much money for a good one.
Eventually after a good test drive I settled on this …….
Its a Mazda 6 2.2 diesel sport model.
Had it just under a year now and it cost me £13500 from a dealer, one owner car with full history.
boot is big(not as big as mondeo) but big enough for us.
It also comes with roof rails as standard which I dont think the mondeo does.
cheers
Steve
EDIT… I also have a springer and he has no probs at all jumping in and out.
It has a flat load bay and the way the rear seats fold down is amazing.
Also has a dog guard /net thing built in.
EDIT AGAIN …
looked at the passat too but it was the most boring car I have ever driven… looks nice though.