There is something backwards about using a solid state preamp with a tube power amp. Why? If there are any disadvantages to vacuum tubes, they are related to the difficulty of driving speaker loads and low impedances as well as the need (in most cases) for output transformers. Those problems do not exist in the preamp where the tubes get to drive a delightfully high input impedance in a power amp. So it would seem that there is no downside to tubes in the preamp whatsoever.
Another thing to consider is that preamps are more about finese, fine detail, and microdynamics while power amps are more about brute force and macrodynamics. This argues for tubes in the preamp and solid state in the power amp rather than the reverse.
From a practical standpoint tubes in the preamp are also much more maintenence free and therefore easier to live with than power tubes, which also cost much more, last less long, make more heat and draw more power from your electrical service.
This is, of course, a generalization and there are surely examples where what I call backwards will work quite nicely, but still the generalization makes more sense.
