Since you are looking at buying a sled and want a turbo, I recommend buying a sled with a turbo on it. You will definitely get a better deal than buying a sled and buying a turbo.
Is a turbo really worth it, that is a very personal decision. It depends on how and where you ride, your riding style, and where you want to go with your riding. It also depends on your pocket book. Have you ever ridden a turbo sled? Have you outgrown your M7? Would a newer M8 or M1000 meet your needs?
I have an M8, I love the power, but really would like to put a turbo on it. but for what I do, I don't need a turbo. I don't pound a hill or a trail, I boondock alot. Besides, if I need that fix, I can jump on a friends TM12 or turbo'ed Apex.
The decision is yours and of course your wife's. She told me she wants a 2013 Polaris Pro 800.