Can anyone help me on Audio Research PH 3SE?

I'm in the exactly the same situation and I use an Ortofon T1000 step-up transformer. You can do better if you get EAR one.
A good step-up device is fare above $100. Otherwise you'll get too much of unwanted distortions and noise from your descent analogue setup.

Limsp,
what version of Helikon do you have? If it is normal version(not SL), ARC PH3SE should have enough gain. I have ARC PH3SE with 0.5mv version of Helikon, Shelter 901(0.5mv) Koetsu Rosewood sig.(0.6mv) and have no problem with gain from PH3SE at all.

Do you know what the dB gain of Classe 47.5 is? does it have balance output option?
Are you using long length interconnect between phono pre to preamp or preamp to amp?
Are you using single ended IC between pream to amp or balanced?

Limsp- Is the problem that with the pre-amp volume control turned all the way up that there is insufficient sound level, or is it possible that you think that the pre-amp volume control should just be at a lower level? Given the premise that "no volume control is the best sounding volume control," turning the volume knob up to a high position is actually preferred. As long as the sound quality is not degraded by excessive system noise, you're better off running the volume control at the higher position. Good luck.

54db is likely the bare minimum gain for a .5mv Helikon.

My system was set initially with 58db and recently jumped it to 64db via a Krell phono stage for experimentation. So far I like what I hear.

If your Helikon is the low output version GOOD LUCK!