First Watt with KEF LS50s

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.