Need help finding a new phono stage.

I just purchased the Marantz tt-15s1.
It has a dynavector 10x5 installed on it.
I have a Cambridge audio cp1, and it sounds great. Which I'm not fully understanding because I thought that stage was for mm only? Can someone help explain this?
My amp is set 3/4 the way up for the volume level I like.. but even at full tilt it doesnt sound distorted or anything!
I guess my main question, and my next step is what is a good phono stage to upgrade to??
For now though I am happy. 
Thanks in advance.