light wheels

have a 2003 330xi on bmw 18's rim's and run- flats. I would like to move up to 19's and keep the run flats (not the ones i currently have but maybe geared towards dry and some wet condition's). I'm dying to get the A.C. Schnitzer type iv but they must cost a fortune and are they light (which would justify the price)? Any feedback on those rims and does anyone suggest something diff. I'm more concerned about performance than look's (i like a simple 5-spoke design)