Non Rega cartridge suggestions on a P6

I used Hana EL on P2 as per recommendation from Upscale Audio. Give them a call. They know what works on these tables 

For what it's worth, I just put a new Rega Nd5 cartridge on my Planar 3 and it sounds fabulous.  You may want to look into the Nd5 or Nd7 as an option.  Is there a reason you want to move away from a Rega cart?

I used a Hana ML on my P8. It required a 2MM shim. I also used the Rega full shim. It is an easy install with just 3 screws to remove the tone arm. Potentially a more solid mount, although would use the split shims if I planned to change cartridges. 

I love my dynavector dv20x2Low on my p-6 and previously loved 20xL on my p-25. To my ears it is awesome. You just need a phono preamp that will accomodate low outpu mc carts. I previously used a Jolida and now use a Sutherland ph3d. And, of course a DV phono stage would be great with it. Good luck and enjoy!