I am in agreement to stay with the Levinson if you like the sound you are getting. If all of them are SS then the sound may vary but IMO not significant enough. Others are recommending tube preamps which will have probably have more impact on the sound which could be more decay to notes, more of a 3D soundstage image, you know what tube do. I don't think you can go wrong with any of the recommendations unless you change to a completely different designed preamp like a DHT or something like that.
Happy Listening.