Since the 450 "exhaust" is on other 700's you know of, then I think it's safe to assume that you are just talking about the muffler, as the the header pipe will not fit.
A muffler is a muffler, they come in different shapes, lengths, materials, etc, but all do the same thing, make more or less noise, and if aftermarket, lean out an engine and do little for performance(efi engines are factory lean for emmisions).
You can run basically any muffler you want that bolts on(just don't use adapters to go to a smaller I.D than the header pipe), but you should get a fuel controller with a Good air/fuel map to richen the mix a little.
It will likely run ok on the stock tune/map, but a decent base map and always a good dyno tune will make it run a little smoother.
Just expect mainly a noise gain, and little in the performance department.
You need a Full exhaust with a bigger air filter and intake, again tuned accordingly, to make any significant and noticeable gains.
Not, it's louder now so it must have more power.