Josh Smith is a better and more impactful player than Jeff Green (who currently makes 9m/yr). I'd take Smith for the price tag of around 12-13mm. it's not quite max but it's pretty fair, i think.
i don't know what trade we can pull off though. i definitely do not want to trade Pierce, (for sentimental reasons). Maybe green, sullinger, lee and a 2nd rounder for smith and a 2nd rounder?