Me personally id go for the skyline if your planning to mod it, you can get alot of power out of it really easly and its great fun to drive espically if you want some sideways fun, my other half used to have a gtst and i loved every second of it, still wasnt as good as my rx7 though
............................................ when it worked lol
My mate has an m3 in the shape you want, great car looks and sounds great too but lacks a turbo, still its quicker than my impreza and has over 300bhp to play with on tap, no lag and is alot easier and grown up to drive cam have alot of sideways fun in it too if you like.
The audi's not really my cup of tea, im sure its still a great car but looks abit boaring compared to the rest.