First Watt with KEF LS50s

First watt is best for high efficiency speakers which kef Ls 50 is not. Crossing over high at 80hz will help a lot.  Could be suitable but probably still not optimal.   Use of subs will make for better results in larger room for sure. 

The F6 should easily drive it and sound wonderful

CRossing over at 80hz still leaves a fair amount of bass up to the low power amp and inefficient speakers. I’d predict sound with less impact or thinner than might be possible otherwise. If you check the audio frequency chart you’ll see upper bass comes into play quite significantly with most musical instruments. You could still well get into clipping sooner rather than later meaning distortion and/or rolled off dynamics at higher volumes. A smaller room would be best suited.

Bottom line is it may be "suitable" but less likely to be optimal.

Whereas two powered subs, ls50s and a high power and current amp would probably perform optimally in a larger room. Class D amps would be a great option to consider.

With no subs. ls 50s are better suited to smaller to modest sized rooms.

mapman, the Reno folks who sell First Watt concur that it's not a suitable pairing.  (I think I got carried away by how well the pair of 20-watt Cary CAD 573 SE tube monoblocks sound with the LS50s.) I sold the Parasound A 21 last night and will use a Proceed Amp 2s until I decide which way to go, i.e., a Halo Integrated or something else.  Which Class D amp would you suggest?

db

Budget?

Also please remind if you tried the HAlo amp with this setup and if so what was the issue there? I would think that to be a very suitable amp in your case.

Though I am less familiar with it the Proceed would appear to be quite suitable on paper as well. I’d be interested to hear how that works out.

If not satisfied with either of these, then I think Class D is a very good alternative to try.