While I'm sure there are other good options, I would second the Bent Trannies. I don't own them but I once borrowed Doug Deacon's and they were awesome. I'm sure Doug will chime in with advice at some point.
On the other hand you might just consider a preamp change. I have a Shelter 501 cartridge which also is .4mv into a Plinius M14 solid state phonostage with MM and MC gain and a LAMM LL2 tube preamp. I prefer to use the MM gain in the phonostage since the LAMM pre has fantastic detail and dynamics and low noise and also using the low gain gives more adjustment range in the preamp volume control. With MC I typically stay below 10 O'clock position.
On the other hand you might just consider a preamp change. I have a Shelter 501 cartridge which also is .4mv into a Plinius M14 solid state phonostage with MM and MC gain and a LAMM LL2 tube preamp. I prefer to use the MM gain in the phonostage since the LAMM pre has fantastic detail and dynamics and low noise and also using the low gain gives more adjustment range in the preamp volume control. With MC I typically stay below 10 O'clock position.