My $0.00005 comments...
I find that the only difference between a 17" n 20" rims is the cost of the tyres and rims. Other than that, ride comfort, fuel consumption, control etc are all negligible.
The new F10 is so fuel efficient that even on 20", I m running on average 10L/100km. Power wise, it is decent enough to outrun a Sonata taxi at a traffic junction.
Have some confidence in the design of the F10, ride comfort wise would not be very compromised when you go on a bigger set of rims, unless your wife and kids are so sensitive to the little dent and humps on the road.
The biggest reward you can look forward to is the awesome sight of the car with the big fierce rims. That is what you want, isn't it? If not, why bother...
Cheers!
