Harbeth M30

I also suggest that you consider visiting the Harbeth users group.

For what it's worth, I switched from the Spendor S3/5se to the M30s. Whilst there were similarities in the overall sonic signature, I immediately noticed a wider soundstage and dynamic range (deeper and better defined real bass, smoother mids & highs). But there are also similarities.

At the time I was driving both speakers with the stock Unico, cardas neutral reference cabling (non bi-wire). I have since switched to a McCormack pre-pro combo.

Noteworthy, the Spendors were originally mated with a NAD742 AV receiver (digital) and, this combination sounded rather muted and dull before I switched to the Unico. It was like night and day.

good luck!

The m30s are harder to drive than the P3s for sure.
Suggest you upgrade your cd player first before changing your amps.
The M30s are more revealing for sure than the P3s since they are more upfront sounding.
The c7es3 are easier to drive than the m30s.

Owning 3 pair of Harbeth speakers (SHL5s, 30, 7s) I have deduced that the 30s need to be treated like monitors....heavy break-in, very careful set up, and to be in close range. They always sound beautiful, but in a normal set-up don't really have that transparent top without being at close range. If you want transparent go with the 7s, which are more transparent further away. The SHL5s are dark and none of them have real bass. so no need to spend the extra bucks. Just get a good and flexible sub.

I've owned both speakers and the M30's were much better than the P3's.  You'll need more power IMO.  I had a Cary SLI-80 for awhile, and after that a Primaluna Dialogue Premium HP integrated.  Both amps matched well with the M30's.  

I wonder if the OP has figured things out already in the last 15 years.