The 17-40mm L is actually softer than the 18-55mm on a 1.6 body, it's a L for a FF ultra-wide not a general purpose lens on a 1.6 crop body. The 17-55mm will be a significant upgrade in IQ and features. Best lens there is for 1.6 bodies.

The 70-200mm is a HUGE upgrade from your 28-135mm, you will be very happy you did.

John.