Think Long.
1. I agree, move away from the Cambridge Duo. I read enough good things, that I tried it, sent it back right away.
All my trials have led me to Tube MM Phono Stages, and since I love my Vintage Preamp’s MM Tube Phono, I prefer to have a separate SUT with optional features for MC cartridges, I highly recommend my lucky choice
https://www.audiogon.com/systems/11318
There are excellent SS or Tube Phono, and units that have both MM/MC, however I have no experience with them, others here will need to help you.
Anything Phono is 'Preferred', not 'Better', so make sure you can return what you try.
Keep listening while you try stuff, don't settle
It’s always good to have an emergency/loaner phono stage, not to mention, the darn thing sounds good, so it helps you compare anything you try. I liked this $16 Pyle more than 4 other mid priced phono stages, until finally the mm/mc stage in my Little Luxman SQ-N150 Integrated Amp sounded quite nice.
https://www.amazon.com/Pyle-Phono-Turntable-Preamp-Preamplifier/dp/B00025742A/ref=sr_1_3?sr=8-3
2. Alignment/Calibration. Is it possible your existing cartridge is not quite right? Who did it? Do you have the few inexpensive tools and acquired skills to mount/align/calibrte a new cartridge? I encourage you to acquire the skills yourself, for the rest of your life.
3. Keep Your Rega until after other changes. Many people like the Regas, and the P8 also has lots of supporters. My problem with Rega’s is that they are fixed cartridges, not removable headshells; made for their ’lower than normal’ cartridges only 14mm high/ and the arm height is not adjustable! So, if you choose another cartridge, you might/will need a shim kit to raise the arm so VTA/SRA can be set correctly.
this shim kit allows insertion by loosening the arm, no need to remove it completely like other shims
https://www.audioadvice.com/products/acoustic-signature-rega-spacer-set-large
4. A different cartridge. (you can move it to any other arm/tt later)
a. MM Moving Magnet with strong output, get the volume you need without noise.
This Ortofon is a good choice
https://ortofon.com/products/2mr-black-lvb-250#specifications
1. R versions are designed with low profile bodies to fit Regas without shims
2. output, very strong 5mv to get you volume without noise
3. boron cantilever, the lighter/stiffer the better.
4. user replacable stylus
b. MC Moving Coil.
After you settle on a Phono Stage/MM Cartridge you like, then you will probably want to try MC. This is when you wish you had removable headshell arm!!!!!!
c. MONO Cartridge. Without a doubt, playing Mono LPs with a true mono cartridge sounds better than playing with a Stereo cartridge with your preamp in mono mode.
Another reason you wish you had removable headshells.
4. Two Tonearms, Stereo and Mono ready to go without hesitation in any listening session. MM and MC both ready to go, Microline and Elliptical ready to go
Once you have two arms, one a removable headshell, the freedom is amazing
I got help here, and ended up with this beauty, for the rest of my life