Take a look at an Atma-Sphere MP3. Uses 2ea 12AU7 and 6NS7's in the line stage. I have one and use GE NOS tubes in both positions. Its a wonderful preamp that will pair up nicely with many different amps, particularly balanced amps.
Sweet sounding tubes for preamps
First, I am a relative novice when it comes to tubes. I have been using LuminX1>Benchmark LA4>Benchmark AHB2>Soundlab, which is incredible with great clarity and speed. Some times, I wouldn't mind some sweetness in the sound (?2nd harmonics), without compromising clarity. I had Don Sachs 6SN7 preamp in the chain and it sounded sweet. I see that some preamps use 12au7 tubes. What is the character of 12au7? Can it give the sweet sound of 6SN7?