Old Polo's are still VW's, where as the really old Skoda's like the Felicia and Favorit, are still Skoda's and not VW's in drag, and therefore probably not very good.

I had a Vauxhall Nova. Not very good to be honest, but probably better than the equivalent Ford Fiesta at the time. However, Vectra's are just Cavaliers in drag. They do have good engines though, good performing cars. They just have reliability problems.

If you are going for a largish engine, you may as well try and go for at least a 2.0-litre engine since it wont be any thirstier than a 1.6 or 1.8 in reality, because it will have more torque and will require less thrashing to get it up to speed.