I’ve used Tannoys almost all my grown-up audiophile life. You should be set with the Fynes! They look like great speakers. I agree you should explore upstream upgrades, as your Fynes can certainly reap the benefits.
I’ve used Rogue gear for many years. Honestly not a big fan of their RP preamp series. Haven’t heard the RP-1, but a guy I trust has said repeatedly that’s a weak spot in the line; there’s a big performance jump with RP-5. So you could jump to that or RP-7 and do quite well. But I’m also pretty confident a used Rogue Athena or Hera would spank any RP preamp. Those were their flagship preamps before RP series. I really preferred that older preamp line.
The ARC Reference 6 is quite phenomenal and would blow your mind. It’s out of your price range, but the 5SE may brush against your upper limit, and is worth a look too.