Prima Luna Vs Accupahse

Seriously there are so many factors (the room being a biggie). In my plebeian opinion putting the Amps difference into very general vernacular, the Focals are fast speakers and the Tannoys (horns) are a bit slower..nay a tad more analog. The same is true for the Amps. The Tanny's are more efficient so to drive.

The sound between A and B will be different. Without knowing all of your equipment opinions as to a way to go are somewhat moot. 

Moving away from the Arcam SA20 w/ either AMP would be an upgrade.

The main reason to consider PrimaLuna is for their all tube design, engineering and overall build quality. It just what they do best. I feel that hybrid “Floyd” offering will be short lived. It’s a nice, all in one package with sufficient power, but the Accuphase (with its tone controls) will likely serve you better across your speaker evolution.

For what it’s worth, I run a pair of Tannoys (Legacy Arden) in my main system powered by the PrimaLuna Evo 300 power amp. It’s a fantastic pairing and I feel like I don’t need to consider “upgrades” in either area. Tube swaps certainly help to fine tune the sound.

Don’t rule the Tannoy Cheviot out when you start to get serious about speakers. It’s a little more affordable than the Turnberry, and the legacy line punches above its weight class sonically. 
 

Best of luck.

You say you want a "rich, warm sound". I replaced a pair of Tannoy Turnberry SE that I had for 12 years and used with many amplifiers/preamplifiers/integrateds with a pair of Focal Kanta 2. Most recent amplification was/is Benchmark HPA4/AHB2, with both Tannoy and Focal. The sound with the Tannoys was certainly warmer, but I'm a lot happier with the Focal sound. Much clearer, much more detailed. More bass (as opposed to "warmth", maybe). In my room, anyway, the Focals have it all over the Tannoys. What am I saying, exactly? I guess partly that you will definitely get richer and warmer sound with the Tannoys. But it sounds much more like real music here with the Focal speakers. Listening to the Scottish Chamber Orchestra right now with them. Beautiful.

I've owned the SA20 and I now own a PL EVO 300 preamp, which feeds a pair of Belles Aria mono blocks.  I'm sure you already know to take advice here with a grain of salt, but I never liked the SA20 because, unlike the broad consensus, I found it very edgy and fatiguing.  So I too was looking to upgrade to a warm, rich sound.  Let me tell you, the Prima Luna preamp was a gigantic step in the right direction.  It is very refined, with a smooth midrange and helps throw out a very wide and holographic soundstage in comparison to the Arcam.  But keep in mind that my amps are pretty rich and full-bodied too.  Nevertheless, I'm confident the PL will help get you closer to that elusive "ideal sound" that we nutty audiophiles chase after.  I've never listened to Accuphase before and have only ever seen anything from that brand during a recent trip to Japan.  I don't know if it will get you closer to Nirvana than PL, but its "cool factor" alone (if that matters to you) is off the charts and would weigh heavily on my decision.  Good luck and happy listening!

I don’t know about the accuphase, but others seem to like it and it has a great reputation. The PL, to me, is a boring sounding tube amp. You can do much better for that money. Do you need that much power? I would investigate PASS, AYRE (both ss) and VAC, if accuphase isn’t already a done deal.