You have a few choices:
1/ Quad preamps. Especially the older ones. Quad amps traditionally had 0.5v input sensitivity and their preamps, like the 33, 44, reached rated distortion at 0.5v out.
2/ Buy a TVC (transformer volume control). This can be used at unity gain or +6db at full tilt. The Django from DIYhifisupply.com is affordable.
3/ Look for a used N.E.W. P3 tube preamp. Modest gain, Cary-built, and quite good as a line stage.
4/ Audion Premier. Their power amps have input sensitivity under 1v, variable by pot, and the preamps are designed for perfect mating with the power amps.
There are others. If I think of them, I'll post more.