To answer the Cardas question yes they are mellow, especially the Golden Refs. Why not sub another IC if you one) and see if they sound better.
For 12AU7s with good definition you want German (RFTs included) if going with NOS . I also love the 7316s for imaging and crystalline top end, but they are expensive.
For 12AU7s with good definition you want German (RFTs included) if going with NOS . I also love the 7316s for imaging and crystalline top end, but they are expensive.