I also like the Stage/Depths. I've been thinking of cutting the black part (aka the tar pit and the confidants) for stage, depths and knight of reliquary in the sideboard. I'm a bit worried of the color needed for Knight, since you want to play it early, but it's quite a good card for our deck.

I could foresee a standard punishing fire list with enlightened tutor and intuition, just cutting the tar pit (cause the stage/depths gives you a reliable kill condition). And the Knights should in theory be pretty good after board, any thoughts?