The biggest differences here are the arm, platter, and motor (power capability). The P3/24 has a substantially better arm than the P1. I think it's worth the price difference alone. You can also upgrade the power supply to the feedback circuit TTPSU.
My take is that if you are at all tweaky, you're going to be upgrading the platter to the glass one, the mat, and maybe the arm wiring. There now you're at the cost of the P3/24. The P5 gets you a slightly better plinth and the same basic arm & wiring with a machined vs. molded base. The P7 and P9 are where it gets really interesting.
I also don't think any of these will outclass the Mira phono stage.
I had a P3/24 and think it's a great value, and excellent performer.
My take is that if you are at all tweaky, you're going to be upgrading the platter to the glass one, the mat, and maybe the arm wiring. There now you're at the cost of the P3/24. The P5 gets you a slightly better plinth and the same basic arm & wiring with a machined vs. molded base. The P7 and P9 are where it gets really interesting.
I also don't think any of these will outclass the Mira phono stage.
I had a P3/24 and think it's a great value, and excellent performer.