Tonearm suggestions

The RB1000 is much better built than the Audiomods, but is more difficult to do VTA as it requires spacers under the arm base. For your deck I think the RB1000 will give better performance. I've heard both arms and would consider the RB1000 to be more precise.
Why not get an Audio Origami PU7 which seems to be what most Palmer buyers in the UK are using. I'ts Rega mount, and I think you could get a new one for US$2500 ex UK or talk to Hammertone the importer. RR $2900 - surely they can do one for $2500.

All the Origin Live tonearms use the Rega mount. So does the JA Michell and other modded RB250/300/301/303 arms.

I am using a Rega 1000 on my LP12. Works very well; I bought the Moth OEM version as it is $1200 rather than $2000; only lacks the Rega logo. According to UK reviews they are identical otherwise. I am using Pete Wriggle's VTA adjustor which will add another $200 or so to the arm cost. I was using a Graham 2.2 previously and it is a good arm also but I am going with the RB 1000.

I dont agree that the Rega 1000 is much better built than the Audiomods. Perhaps Dover can explain. Everything about the Audiomods that matters is top drawer, from bearings, to micrometer VTA adjustment to VTF accuracy. And its cheaper.

You mike look into Helius Omega also. Excellent arm, unique bearing system and sounds as good or better than my SME IV.

Very excited for my Audiomods with the micrometer to arrive. Dover, good to hear your thoughts on it vs the 1000. I'd love to hear are more detailed comparison of the sound.

As far as other Rega issues here, be aware that the Rega built arms not labelled as Rega don't always use the same wiring that Rega uses. Sometimes that is very visible in the RCA connectors used. Not that there aren't tons of rewire kits out there.

The Audiomods has the excellent micrometer VTA options, but for other Rega arms without easy VTA adjustment there are good options such as Pete Riggle's VTAF.