A turboback exhaust is the whole exhaust, from the turbo back (including the downpipe) . Therefore it replaces the catalytic converters. A catback exhaust only replaces the exhaust from the catalytic converter back, so it does not replace your stock catalytic converters.
Newer model WRXs occasionally have problems with boost creep when running catless exhaust, so you should be looking for a catted turboback exhaust. (Not to mention the Cobb maps are designed to work with catted exhaust only)