Personally, I think "congested" is rather the opposite of "clear separation", which means things sound bunched up and less distinct.
And to me, "Small soundstage" means either less left-right separation, or less depth to the sound. Compared to some other amps in the same league ($200 and below), I can say E12 is behind C421 and C&C BH when it comes to soundstage. Specifically because left-right separation isn't very wide. Depth is very good on E12, though, and it conveys very good mental image of the sound.
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