First Watt with KEF LS50s

If the powered subs are doing the work below 80 hz my guess is it would be suitable. 

As great as the First Watt amps are, I think that they might be a bit underpowered for the LS50s to sound their best. So I'd go for the more high powered models in that line.

I'd also recommend talking to Mark at Reno Hi-fi if you don't have a dealer in your area. He has a good return policy that will permit you to hear for yourself. 

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.

If you mean a Halo Integrated amp, the answer is no.  I've used both an A 21 and A23 to drive the LS50s, and much prefer the A 21, but it's too large for the cabinet I want to use so I sold it last night.  Richard Schram tells me the sound with Halo Integrated should be closer to that with of an A 21 than A 23, so that's a strong recommendation.

This is a secondary setup that's in use most of the day, so a low energy Class D amp could be attractive.  My main setup uses three JC 1 monoblocks for LCR and two A 23s for surrounds.  I have three Proceed Amp 2s sitting on a shelf that as I recall, are fine amps, but an integrated or Class D is an attractive idea.

Budget?

If an integrated what other features might be of interest? That’s a big factor there. Some I find of interest are built in DAC, phono, headphone amp and even Bluetooth.

dbphd I would consider an integrated if that add any value for you even more than otherwise if a Class D integrated. I have Bel Canto c5i and have heard others like Rogue Sphinx and Pharoah and am pretty convinced separates no longer offer the same advantages they used to over integrated amps in terms of noise levels and distortion. The c5i integrated gives up nothing to the Bel Canto ref1000m amps I run in my main larger system in this regard. The next amp I get for that may well be a Class D based integrated amp as well something along the line of Rogue Pharoah or whatver the latest and greatest may be when that time comes.

I think I would use only the balanced input, perhaps with a Goldpoint to switch between an Oppo BDP 105 and Sony HAP-Z1ES, both of which sound better with balanced output.  It would be nice to have an HDMI option, but HDMI seems a can of worms small companies fear to open, although Bryston seems to have done HDMI pretty well in my SP3.