Gain Question

Do you want it to be louder? If not you actually get the best sound with the volume control at or near maximum. If you don't want it to go louder you are in an ideal situation.

Your phono pre has quite a bit of gain so I suspect a step up will overload it. You need to fix it elsewhere.

I trust Almarg's math so if you do want it louder you need some more oomph from the amp. Since you are getting enough gain to get close to 2V into your amp if you want to go louder you have to get an amp that can get more power out with that input. Your low efficiency speakers simply need some more power.

You don't "need" to run the MM into the MM input. You could try it into the MC as long as the phono stage has enough headroom. It would not be ideal since the MC input wouldn't have the capactive loading that the MM wants to see so not a permanent fix but an interesting experiment that can do no harm. As long as it doesn't clip, or maybe even if it does a little it would answer the question of whether or not you have enough gain prior to the amp. If you use the extra 20dB of the MC input AND it doesn't grossly clip AND that gives you the volume you are looking for then you would know the amp is capable as long as it gets a bigger input signal. If it is loud enough then you need to get the gain somewhere else. You're not going to find a phono stage with significantly more gain so that leaves a higher gain preamp if you want to keep the amp, or an amp with higher sensitivity, or a combination of the two.

Many preamps have gains over 20dB which looks to me to be the ultimate solution as long as 120 watts is enough to get the speakers where you want them, and I suspect it is. . You could also search the classifieds for a fair price on a preamp with 20+ dB of gain and try it. You can sell it if it is not the sound you want but that would also answer the gain question.
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