If you really want an end game phono stage, then go try some valve one’s.
I have i believe my end game phono stage now, the absolute stunning allnic h7000, now with an even better valve in the power supply.
I use a Gold Note PH-10 (together with the additional PSU-10 power supply) with my P8/Apheta 3 with excellent results. In addition to the sound quality it’s controlled via a single knob (and display) on the front, making it eminently easy to make adjustments on the fly. It has a number of gain levels and load options to enable a correct match to virtually any cartridge.
Installed a Allnic H1202 phono stage in my system on sunday. Had a Parks Audio Puffin before. Huuuge upgrade. So much more clarity, dynamics, microdetails etc than before.
Use more money that you can afford in a phono stage if you play a lot of records. It is worth the money. You gotta pay to play.
TomTom Audio have a Stageline S for sale at £300. I have no idea if that would suit your Rega cartridge. But I’m sure that James Allney there could find you different boards, if necessary.
Of course, it may be be a lot cheaper to fit internal 523 (?) boards to your NAC252.
With my P10, Apheta-3 and 252 I had an Aria, then a SuperLine, and for all the love people have for the Aria, I found the SuperLine so much better in combination with the 252. Of course it’s much more expensive as well but I got a great used one that wasn’t. Don’t believe the nominal loading values though. I use the 500R and 1 nF with the Apheta-3.