IMHO, not enough gain in my Phono stage

You have mis-identified the issue. I would argue that your system has too much gain for your CD not too little for the phono. In an ideal world you would have the volume turned up to full blast just as it reached your desired volume level. Having the signal go through any volume control degrades the sound so the closer you have it to full volume the better the sound.

It sounds to me that you are using a passive linestage or a linestage with no gain or very little gain. I have a Rotel phono stage and when I used it with a linestage with no gain I experienced the same problem. My preamp is a VanAlstine Super PAS3si tube unit. I have since switched to a Hagerman Piccolo step up or headamp with gain settings and cartridge loading. It plugs directly into my tube preamps phono stage and all my problems with gain have been solved. With my existing phono stage having about 40db of gain the Hagerman gives me settings of 12, 20, and 30 db of additional gain. I choose the 12 db of gain and provides more than adequate volume.

I'm using an Audio Technica OC9II ML (0.4mv) with a Rega RB 600 tonearm. I have tried the 20db but the sound quality is better at the moment on the 12db and 100 ohms loading. I love that flexibility. If I play a record with lower gain and I need more I simply select the setting I want and in seconds MUSIC!

This was an example of how the linestage and gain play a role in the volume of your phono stage. The Rotel should be the gain of 40db MM or 5? or 60db for the Rotel PLUS the gain of your preamp or linestage.

Unless you have an ARCAM rPhono with an MC gain of up to 82 dB, it is best to use a line amplifier such as the BERESFORD TC-780LC.
I use an AUDIOLAB 8000A to amplify the signal from the CAMBRIDGE AUDIO 651p, using the AUDIOLAB PRE-OUT output to my main amplifier, through which audible signal degradation is very difficult to notice.