While I've never tried it with a Hartke, I have used an Alembic pre with other power amps with good results. You could just run the F1X into the power amp in of the Hartke and bypass all of the Hartke preamp electronics. I guarantee it would clean things up.
But as has been stated, Alembic pres are very clean. There's lots of discussions in the forum about tube amps, etc. so look around and see what people have said. For a grungier, more classic tube sound, maybe try Ampeg, although personally I find that tone to be annoyingly wooly. the other thing to remember is that if you go through the PA most of the time, the DI on the F1X is excellent and all of that good tone will be going out to the PA system, so the audience will hear the good tone.