If you buy new, I would think you'll have to wait out the cycle for the new tank.
I think that's probably the easist method, work wise.
You're ability to transfer your current substrate depends on the type. If it's DSB, I don't think you can. Otherwise, I see no reason why you couldn't.
I'd get a tub, move your LR and corals to the tub (with water from your nano).
Then move the substrate to the new tank.
Then put back the water (plus some new water), and your LR and corals.
Such a quick move will be of very little stress to your critters.
But an easier solution might be to just get scratch kits. They require a little elbow grease, but fix up your scratches pretty good.
If you're gonna move to a new tank, why not go bigger?
