Cartridge for a Rega P5?

IMHO, not the 103, as it really sings best with an arm mass over 14 grams. I would cast my net a bit wider and include the Dynavector 17D3 and 20XL as they mate very, very well with the Rega arms.

Rega Exact 2...........
There's a pretty magical synergy between Rega cartridge, Rega arm, and Rega table. The music sounds simply wonderful with this combination. You'll be quite happy.
Good Luck, and Happy Listening.

I've tried 2 Rega carts including their top o'the line Exact and I was very unimpressed with either one. They're easy to set up... and that's the end of the list of good things I found to be true about Rega carts.

The P5 is a good turntable, go for a Dynavecto 20XL, Ortofon OM2 Black or similar.

I've used a Denon 103R and a Denon 103D on a Rega arm and it worked fine, but it was better with a headshell weight attached.

I also recommend the Dynavector 20XL