Which generational gap do you feel was the last big leap in audio?

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In hindsight, maybe I should have gone further back with the poll, based on answers so far!

I voted 6th to 7th; I remember being wowed by how much crisper sound effects were on my 360/PS3 than my OG Xbox/Gamecube back in the day, presumably cos you can fit higher quality sounds in 512MB of RAM than you can in 40/32/64MB.