Cartridge output is 1.5mVFirst, I suspect that you mean 0.5 mv. As far as I am aware Grado has not produced any versions of the Sonata having rated outputs of 1.5 mv.
Second, 54 db gain is much higher than is typically provided by phono stages intended only for MM applications. It is roughly mid-way between the typical gains of MM and LOMC stages (and actually a bit closer to what is typical of LOMC stages), which suggests that the PH3 is likely to be suitable for use with many LOMC’s.
Finally, from the description of the PH3 at arcdb.ws:
Used with typical line preamplifiers having 12 to 18 dB of gain, the PH3 is suitable for phono cartridges having .25 mV output or higher.So my guess is that you’ll be fine.
Regards,
-- Al