Do u mean it's rubbing on something inside? If so, your wheel offsets are probably wrong...no amount of alignment will solve ur problem...find out exactly what width ur wheel is and offset and I will tell u if thats your problem...
Did it occur to you that you could have replaced both the fronts with a cheaper option? I'm not talking about cheap and nasty stuff either...
Cruzen - posting some pics of your wheel would help. Apart from being a Japanese made rim, it probably all comes down to whether they look good or not to fetch a decent price.
20s are nice but as mad mike pointed out u will lose a bit of ride comfort. Check my topics, I have a set of 19s that would suit your sedan nicely if u want to preserve the classy, euro look instead of race look.
U don't need a trip computer to work it out. Fill her up full, reset odometer, drive, next time you refill, make note of how many litres u fill up, the divide litres/ km travelled n u get ur consumption.
I am one to also say it's your car do what you like and not what others think....in this case however...do not do what u like and listen to everyone on here. I wouldn't put tht on my car even if u paid me to.