I'm ignoring the jacket to note that such an aggressive spread/cutaway collar doesn't look good on you here; the strong, almost horizontal line conflicts with your relatively thin/trim form and doesn't look harmonious. The jacket's trim cut exaggerates it in an unpleasing way.
You bring up a valid point about pairing peak lapels with a cutaway shirt. I was actually at SS on Saturday looking for a cutaway white shirt to match the peak lapel Washington suit for my wedding. After discovering SS doesn't even carry a cutaway shirt in white I then realized with my peak lapels, it might be a better idea to keep the rest of my wedding attire much more subtle and understated. This includes my dress shirt.
I ended up with with a semi-spread collar and they gladly darted the shirt for $8 bucks. True, a peak lapel suit isn't exactly the classic choice of suit to get married in however it was a personal decision :)
BTW, I know I promised to upload pics of my two Washington suits however I decided to go back and have both suit jackets taken in at the side seams. Once I get the jackets back I will for sure upload pics.