Barnes and Speights for Bass.
The salaries match almost exactly. It doesn't save much money next year (a couple hundred thousand), but if you'd rather have Barnes than Bass going forward, I think it's a deal Golden State would do that doesn't cost any draft picks. I guess how willing the Celtics would be to do this deal depends whether they think Barnes can be a building block or not. He's been mediocre so far, which is why GSW would move him, but maybe a change of scenery would help.
The downside of top 10 picks is when they don't perform, their salaries become burdens.