combination tube amp and ss preamp?

there are many combinations that can work well. Warm meaning??? Reducing noise can provide a warm sound, Conrad Johnson preamps and amps can provide a warm sound, some SS mosfet amps can produce a warm sound. You need to try combinations for yourself.

Why would you want to do a horrible thing like that? got a cheap one lined up?

Almost joking here.

Most people do it the other way around a tube pre with a ss power amp. That way you get the warmth from the tubes but still have the bottom end grunt of a ss power amp. I have one system setup that way and it works very well for me. I have never even thought of going the other way....

Agreed with Joekapahulu. Since the pre is the heart of your system and generates the signal that will ultimately be reproduced by your speakers, having a tube pre makes more sense.