@hsv pretty much summed it up. The SportKa is indeed the sporty version of the normal Ka. The StreetKa, I'm guessing, is just a play on the expression 'Street', as in it's cool. The StreetKa is an awful car though, having gone through the normal process that a car does when it has its roof chopped off, it's a good lot heavier than the Sport and as such loses the benefits of the uprated engine, tyres, suspension, etc that the Sport has over the regular Ka.
The Ka in the game is the original launch car, and I think the model is broken as well. I'd be happy if they added the later models that at least had colour codes bumpers and of course I'd love PD to make it drive like it does in real life. The regular 1.3 Ka is a hoot to drive as it is, obviously the Sport with its 1.6 engine and fantastic gearbox adds to the go-kart like handling, making it the awesome little motor it is.
Ford has the technology and the know-how to make a real good Sport version of the current model, I just can't see them doing it, with the way manufacturers these days chase MPG and CO2 figures, plus I doubt they'd want to take sales away for the
Fiesta ST-2, which looks set to become a legendary car itself...
{Cy}