Ignore the Metro bits on above. You take the Metro green line to Regent Centre then either X11 or X24 to Plessey Road.
Definitley, getting off at the Regents Centre cuts your metro journey in half. If you were to go all the way to the Haymarket you would still pass the regent centre on the bus only you'd be adding at least 30 minutes onto your journey.
Definitley don't go to Sunderland though as its considerably out of the way.