Is this the look you're going for? As someone with 19" wheels, I love the size and think its about right, 20" looking a tad aftermarket (I'm no aftermarket fan unless its spot on and looks like it could have been OEM). 19" wheels reduce ride comfort, hit even a slightly crap bit of road and the car starts jittering and rattling. Something that the 18" wheels, just for that little extra rubber, help with. I can't imagine how the ride would feel on 20" unless you only drove freshly laid spot on roads, here in Manchester 20" wheels would either be destroyed or the suspension would be knackered in no time with such a tiny amount of rubber to protect the wheels/suspension. ** edit, you'd likely also be fed up with being thrown around in the cabin in no time, or stopping to get over feeling sick now and then given you'd likely have to also stiffen up the suspension too.