Cary's SLP-05 fits the bill, though sans HexFred - which can be DIY fitted. The SLP-05's off-board power supply with its rectifier tube is the icing on the cake.
The 12AU7 and 6CG7 have very similar characteristics to the 6SN7, in fact the 6CG7 is the exact same plate structure as some NOS 6SN7s. But 6SN7s usually sound better, I think its because of the base, which is less microphonic.
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