IMHO, not enough gain in my Phono stage

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.

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.

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.

Put an attenuator in the line from the CD player if the difference bothers you and you are not having noise problems. Otherwise the Creek 15 phono stage or at a higher price the ProJect Tube Box 11 SE.

One effective,easy, and inexpensive solution for the different level issue between phono and CD is to use RCA phono attenuator plugs in line with the higher level CD IC to lower that level more to the level of the phono. I've used Harrison Labs 12 and 3db attenuators both separately and together for a similar issue with excellent results.

http://www.amazon.com/Harrison-Labs-Line-Level-Attenuator/dp/B0006N41B0

how much do you want to spend? There are some phono pres with adjustable gain that can neutralize the problem you have though it may not be optimal for sound quality vs turning your volume up on your line stage.

I like the Jolida JD9A which can be found new on ebay for $379. I'm not aware of any units for less that have similar gain.