Naim vs ARC

A bit of an upgrade dilemma and I hoping I can draw on the experience of Naim owners.

The Supernait has been a great simple amp. But I have two issues.

A side from the hicap, there isn't really an upgrade path.
Some female vocal recordings can sound a little harsh.

I have been googling for a while and can't find any comparison between the naim supernait and other brand gear.

The Audio Research combo is SP2 and VT50 power amp which is available at a similar used price.

Other parts are naim cd5i and Spendor sp2/3r2 and chord sig cables.

Please keep this discussion about upgrade experiences :)
On a completely separate note, how do you like the Spendor 2/3r2? I heard some recently, really like them and close to pulling the trigger on a pair. What are your impressions of them?

I don't see a lot of comments on the 'Gon or elsewhere about them. There are a lot more folks in the camp of the Harbeth 7es3, their direct competitor. The Harbeth is a fine speaker for jazz and classical and of a similar ilk. But I listen to more rock and reggae and the Spendor seems to reveal more soul and oomph.

I'd be pairing them with a Rogue Cronus Magnum/Rogue Ares phono pre, and they seem to be tube-friendly, I believe.