Is the Sovtek the LPS variant. Those have a good reputation for being clean and quiet with high gain. They are not known for their Bass however which is kind of interesting. Since it is a phono pre I think you may just be better off with carefully selected current production tubes. NOS tubes are just not plentiful enough to find really quiet ones, with a couple of exceptions like Upscale, new production tubes can be screened in large batches and thus as a rule can be super quiet. If you can afford them the GL reissues are getting some good reviews for their tone. They should still be less than really good NOS. Jim McShane over on Audio Asylum can set you up with good ones.