Jen, the Blue Daze does best if it gets quite a bit of sun, but the Spaths need filtered shade, or just morning sun. So if you're wanting a mixed border you might not do well with those two planted together.
But the Spaths would interplant beautifully with Plumbago because it doesn't mind some shade. Other than needing a little pruning to keep it in bounds, it's an extremely easy plant. I've seen both for sale at my local Lowe's pretty often.
Bottom line, just be a little careful mixing your sun lovers with your shade lovers in a border. Somebody's going to be unhappy.
