The M3 is a fine preamp. I know it's sound well and I have used two different AI preamps over the years. My comments are not meant to suggest that the preamp is anything but very good; it obviously is, given it's success. But, to answer the OP's question, I will try to offer some impressions of it's sound compared to the CJ sound, and here is why it gets tricky to describe sound in a way that is meaningful to another listener.
I will preface my description by simply saying that, to me, a PV11 or PV12 sounds more like what live music sounds like than the AI A3. The CJ sound is often described as "dark"; whatever that is. I disagree. If anything, I find the AI sound darker. With the CJ's, individual images have more natural color ("darker?") vs. what I hear as absence of natural color from the AI. To my ears, the CJ has a more refined sound. I hear more grain in the AI sound. The AI presents larger images with greater stability (reach out and touch). But, the CJ's give superior rendition of dimensionality with less grunge in the empty spaces. I think the AI's images are too large, and the bass is a little too thick, and then there is that somewhat "bleached out" tonal quality; while the CJ's may sound a little too "golden" for some. If I had to choose, I would choose a little too much color over NO color. Music has A LOT of natural color. Lastly, I find the AI sound dynamically polite compared to the CJ's naturally lively quality. The AI is quieter with less background noise.
Good luck.
