Have a look at VTL's pre-amp. IMHO their pre-amps lean to the bright/clear side of tube pre's. Also take a listen to Mcintosh's pre's.
What are the more subtle sounding tube preamps?
I mean "subtle" as in relatively less tube saturation or color than your average tube-pre. Common sense tells me less tubes as in a single dual-triode, but in reality that may not be the case. I currently have my eye on a CJ Classic. Not sure if that will fit the bill. Any suggestions welcome.