v6 and v8 are the same but you can get adjustable ones. some people say they are wank some people like them. i have one in my vr stato 5ltr i think it did it some good. but im not gona tell everyone they are the best thing for your car
Around town you would never notice the difference, so as above only spend the money if you do constant hills/twisty road driving or take the car to a track or hill climb type event.
Also, if you buy cheap ass Bob Jane special tyres, again do not bother. I don't understand people that spend thousands on their suspension setups and then go out and buy the cheapest possible tyres, when it is arguably the tyres that make the most significant difference to the handling of the vehicle.