Instead of specific models, here are some companies that produce excellent sounding, and extremely well made tube (pre)amplifiers. Find a used one made by them within your price range and really cannot go wrong.
Art Audio - dm-vps
BAT - VK-31
Cary - SLP 98L
EAR - 834L
Modwright - swl9.0se
These are all very, very, good tube preamps still in production and made by great companies with excellent customer support. All a larger, well established, manufacturers.
The Thor mentioned above is guaranteed to a be great unit, but the creator just shut the company down unannounced 2 years ago and walked away hanging everyone, from dealers to customers, out to dry. It was bought by the two guys that own HighEndAudio.com and they have reintroduced the brand and (I suppose) service legacy products. You can read about it here - The Return of Thor Audio: An Interview with Ted Lindblad of High End Audio
Art Audio - dm-vps
BAT - VK-31
Cary - SLP 98L
EAR - 834L
Modwright - swl9.0se
These are all very, very, good tube preamps still in production and made by great companies with excellent customer support. All a larger, well established, manufacturers.
The Thor mentioned above is guaranteed to a be great unit, but the creator just shut the company down unannounced 2 years ago and walked away hanging everyone, from dealers to customers, out to dry. It was bought by the two guys that own HighEndAudio.com and they have reintroduced the brand and (I suppose) service legacy products. You can read about it here - The Return of Thor Audio: An Interview with Ted Lindblad of High End Audio