Tvad has read my mind. To get what you are looking for I'd suggest your considering some older, perhaps even vintage, pre-amps even if you have to have them reconditioned. Early ARC like my SP10II might do, or MFA's or CAT's which were close to SOTA in the late 80's thru the early 90's. Some good CJ's too.
If that isn't your cup of tea then consider matching a currently high end tubed pre such as those from Lamm and focus on getting all of the rest of the sound qualities that you want from a tube amp. At least that is I would do. A great neutral pre-amp is ageless - even my old SP10 sounds dammed fine but it has been bettered in transparency in its line stage which improves soundstage depth.
FWIW.
If that isn't your cup of tea then consider matching a currently high end tubed pre such as those from Lamm and focus on getting all of the rest of the sound qualities that you want from a tube amp. At least that is I would do. A great neutral pre-amp is ageless - even my old SP10 sounds dammed fine but it has been bettered in transparency in its line stage which improves soundstage depth.
FWIW.