Brewing Series

I really liked doing a series of brews using the same yeast cake. The fermentations were excellent and quick, so I'm already planning on my next series. I haven't brewed anything Belgian in a long time, and they really like to have lots of yeast pitched into them, so I think it's about time.

I'm thinking something along the lines of doing a relatively weaker beer, then a mid-strength beer, then something uber. Maybe do: Belgian brown (5%-ish), a dubbel (7%-ish), and finish with a quad or a dark strong or something similar (9-12%-ish). Style, yeast and recipe suggestions are always welcome. Obviously I'm going for a series of dark beers, but I could just as easily go light (pale - blonde - tripel?).