Rega P6 cartridge upgrade

I am happy with my nd5, you could try the Nd7?

 but I now live 6 hours away from NJ

you also live 6 hours from the UK :)

What is your goal for changing the cartridge and what phono stage are you using?

I also have a P6 and my first cart on it was an Exact MM - loved it! Switched to an Ania Pro MC - loved it even more! I was pursuing detail and soundstage over slamming impact (which I also appreciate), so I went for a Dynavector XX-2A. It has been truly enlightening so far. Amazing! Depth and detail for days.

For the record, my phono pre is a Sutherland Little Loco, so I went for the XX-2A since it was reviewed as being a good match for the Little Loco, thanks to its very low internal impedance. So YMMV depending on your phono pre, of course. Also, I'm not using a spacer and the Dyna seems to track just fine. 

I have owned both of the cartridges the OP mentioned. Both are very good low output MC carts.  I slightly preferred the Dynavector but either is good. What phono preamp and/or SUT are you using? I used a PS Audio Stellar, then a Sunvalley, then finally a Hashimoto HM-7 SUT into my integrated amp’s MM phono input.  All were good, but the SUT into MM phono was best.

If you are in the metro west area of Boston, try Natural Sound they have been a Rega dealer forever, as someone else pointed out Fidelis in Nashua NH, also a very good shop.