Seems there's enough variability in our cars across enough areas that it makes it hard to say definitively whether the 205 is going to stick out too far with a 6" wheel and ET20. Also, some 205's are wider than others...seriously.
I will say that you can run 195's square on 6"f/7"r wheels and have a very good handling (relative phrase) Tiger. You can also get good 195 tires (Toyo R1R, Dunlop Z2 Star Spec) in a 55 aspect ratio, rather than 50, which gives a little more sidewall and diameter. In the 195/50-15 size (or 205/50, for that matter) you have tons of choices, including the newest generation performance tires.
I will say that you can run 195's square on 6"f/7"r wheels and have a very good handling (relative phrase) Tiger. You can also get good 195 tires (Toyo R1R, Dunlop Z2 Star Spec) in a 55 aspect ratio, rather than 50, which gives a little more sidewall and diameter. In the 195/50-15 size (or 205/50, for that matter) you have tons of choices, including the newest generation performance tires.