For a remodel, a one-piece would be a tough install. We install them in new construction when we can get in before the walls are all up and the electrical hasn't been strung yet.
You could also consider poured marble products if you want to go wider. It can be made to fit, and is very durable.
Or picking up a fiberglass pan and tiling the walls is an option too.
The Sterling kits are pretty nice if you don't want to spend much and don't mind drywalling over the flange.