Why are you removing the sub floor? This is rarely necessary.

@joseph corlett, LLC: the subfloor is damaged. The floor has been uneven since we bought the house 19 years ago. We're only now getting around to doing something about it.

@Cabot & Rowe: we'll be working with some contractors, but purchasing most of the supplies ourself. I'm trying to come up with materials estimates and thus my question as to whether we'd need both sub-floor and backboard or just one material that could meet both needs. You've answered my question masterfully. Thank you!

And PS we're also putting electric radiant heat beneath the tile...

Then use a product like ditra heat or a warm wire which then gets covered with self leveler.

Subfloor and backerboard/cement board/underlayment/Ditra (<--best option) have two different functions, and yes, you need both. The heating wires and leveler, if needed, go between the subfloor and underlayment. C&R's first post makes it sound like you need cbu + membrane (Ditra), but this isn't the case.

Sorry, but if you have to ask, you probably want a professional to put the materials list together for you....