But I think 'dark place' isn't a matter of good or bad/positive or negative. It serves a psychological and metaphorical purpose that Spike has long been alloted.

See, I think it's both psychological and that's why it's intimate, because he's so close to her. But he's also his own man here in his return. He's not the mindless dark desire, but he's also the one who reasons and logics and detects. He's the dark place and he's also the light of reason.