I have 18"s all the way around but kept overall tire heights the same so I still have the larger in the rear look. I would have preferred 17's in front and 18's in the rear but could find the wheels to do this. I moticed and improvement in the rear by reducing the unsprung weight. The car doesn't get that unsettled feel on bumps any more. 17" wheels will clear the stock brakes just fine, not sure about SRT front brakes though.

My 18's are staggered. 8 inch wide in front and 9 inch wide in back. With 18's in the rear I think the perfect tire is a 265 40 which is 10mm wider than stock and only slightly taller than stock.