From B&W 804 D3 to Focal Sopra 2?

Go hear the Borresen X1 monitor with matching 

Stands  I have heard them all before 

A sub is needed if you want low bass 

The Borresen is by fsr the best tweeter

That ribbon is open and airy

Another speaker perlisten R5 in the $6k range also with stands 

2 exceptional speakers that ate a much better value 

And at least as good ,

I think that the your Anthem will power the Sopra's just fine.  I'm driving Sopra No2s with a Hegel H590 (300w/ side, dual mono) and it's never clipped or run out of headroom.  

B&W vs. Focal:  I disagree with some of the comments, I'm in the camp that the Sopra's will be nice step up sonically.  It's a much more robust speaker, better crossovers, much more substantial cabinet (for better bass).  The B&W weigh 73lbs the Sopra's are 120lbs.

Having said that, you have a very large listening space and it will be challenging for any speaker that size to fully pressurize it with bass.  Subs are an obvious option or perhaps consider the larger Sopra No3.  Good luck and cheers.

I’m running sopra 3’s with a 300B 18 watt and the top of the line Luxman M10X.

the secret is a good power supply. Both sound awesome just different presentations.

I tried to find the Sopra 2 imedance curve but I couldn't find anything. If the impedance drops down low (2 ohms or so) for much of the audio band then you would need a very robust amplifier for them to sound their best. Your Anthem is rated for 2 ohms and increases its power with each halving of the impedance (400 @ 8 ohms, 600 @ 4 ohms, 800 @ 2 ohms) but it does not have the balls of a Krell or other monster amp.

Assuming that the Sopras have a reasonable impedance curve then your Anthem should work very well. You would have to spend huge bucks to get an amplifier with more current than your Anthem.

I have a the Sopra 2 fed by a Hegel H390, 250 watts at 8 ohms.  PLENTY of power.  Room is 17X28.  Smooth, clear, extended and quite fast and detailed.  Chopin to Foo Fighters, Susan Tedeschi to Snarky Puppy .  Always dynamic and, most importantly, engaging.  However, there is also a pair of REL low frequency speakers.  (REL doesn't like to call them "Subs" because, as they correctly point out, sub-sonic speakers produce sound outside of the range of human hearing.  Hence the term "sub" as in "sub-sonic".)  My primary use of the RELs is not to fill in the very bottom 15hz in the music, which they do admirably, but is to relieve the main speakers of the responsibility to deliver fully their last 15hz, give or take.  All speakers roll off as they approach their bottom.  I have the RELs set to start engaging at around 50hz, I'm guesstimating.  A number of people here are suggesting low frequency support.  Don't brush it off.  Sorpra/REL combination is a good one.