I personally can recommend the Fender TBP-1 and Eden Navigator preamps, both tube, although the eden is much less vintage in it's tone and less "Tubey" sounding.
To be honest though you read a lot about how you HAVE to have tubes in your amp for it to sound good and fatten up the tone, but that really isn't the case at all. there are many great Solid state designs that sound fatter and better IMO than many of the tube ones. Sure if you are gonna be laying down serious dough for a top of the line piece of studio equipment then you may very well hear the difference but at the price point of gear this thread is discussing, I don't think you should limit yourself to tubes only, because in most designs preamp tubes don't really even make that much of a difference...
if you were talking about tube power sections, that is a different game. Just saying, don't look over some really great pieces of solid state gear just because you heard somewhere that tubes are better...