X3 2.5 Tire/Rim size

[MyX3]

I just bought myself a 2006 X3 2.5 (Im in Europe so they still sell it here), I ordered it with 18 inch rims. I am a bit unsure if the 18 inch rims will affect the ride negatively in any way. Anybody out there who knows?

One of the sales people told me that it requires a powerful engine to have 18 inch rims anyody know if thats true and if so, does the 2.5 have enough power for the 18 inch rims.

Thanks for your help.