High gain preamp?

Anyone recommend a (£500’ish) preamp to drive the First Watt F4 amp?

It’s a unity gain amp so needs a preamp with 20+ dB of gain and a voltage swing of 14V

M7 clone

World Designs Pre3 might do the job if wired for higher gain.

Loads on DIYAudio use the Korg preamp which gives that 2nd order harmonic thing.

Nobsound M77?

Dunno about £500, but an AudioValve Eclipse can, with gain to spare.