Of course you sacrifice tire wear by not being able to rotate tires, if you're wider on the back. All depends on how deep your wallet is and what your prioroties.
I see people complaining all the time about the 245/45/20s being "too skinny". For every day driving, there's nothing wrong with this width. Now if you're going to the strip, or the track, you may want more rubber on the road. But get out your calculator, calculate your contact patch on a 245 and then on a 255 or 275, compare to the weight of the car, and see if you think it's worth the effort and money.