I don't understand why you'd consider V3s if you already want to change the springs on them (and before driving them?).
Either way, the Swift spring conversion is meant as an upgrade for those who already have V3s; it seems pointless to me to buy V3s just to do that.
Also I find it difficult to make any kind of recommendation whatsoever (kit/spring rate/camber plate/ etc) when you don't even provide any kind of info whatsoever about the use you have for the car.
In any case, V3s ride pretty smooth. The CS are a little stiffer but still plenty streetable imho.