Amplifier ideas with KEF Reference 1

keoliphant, Bel Canto has told me that the Black EX separates will play to a higher level than the ACI 600 as long as you make sure you're using a very high quality XLR cable between them.

You seem to have a lot of expert advice. I have owned many Kef's and the magic mid is the take away for me.   

I'd concur that some recent integrated amps may be the ideal choice to support the great mids.   

You should also audition the Constellation Integrated 1.0 and the Moon 600Vi2.   

Interesting posts by all. Thanks for the dealer participation by @audiotroy  and @everest_audio  and their individual takes on the OP's questions/situation.

@keoliphant   Sounds like you have made a choice. I'm interested in hearing how the amp-speaker pairing work out in your office.

 All the best.

Thanks for everyone's input. I just started a new thread specifically on the aci600 vs Black EX separates..... Hoping to learn more. I'll report back once the system is in place!

@keoliphant
If you can find a pair of Classe Delta CAM 600 monoblock amps try to have a listen to these amps in your own setup and system. These amps have been discontinued last year and few Classe dealers might still have them on display or in b stock and they can be had at discounted price today. Their original retail price was $14k/pair. You can still keep using your PS Audio BHK Sig preamp and Direct Stream DAC.

The Classe Delta CAM 600 monoblock amps are class AB design and huge and heavy but they run cool due to superb internal heat management system they have in there. Classe uses ICE Tunnel to dissipate heat which is executed outside the signal path and does not interfere with the amp's circuitry. 
These amps sound and perform phenomenal very musical very smooth refined and doesn’t get in the way of the music. The amps don’t induce its own sonic coloration like some other high end amplifiers do. Your speakers simply sound like themselves. You should read reviews on these Classe CAM 600 monoblock amps. The Classe CAM 600 monoblock amps received many outstanding reviews from several different hifi reviewers from many different hifi magazines and sites. John Atkinson of Stereophile simply said that these are the best sounding amps he's ever reviewed or the best amps ever made period. I know it was pretty bold statement he made, and one reviewer from The Absolute Sound made similar statement regarding these Classe Delta CAM 600 monoblock amps. 
In reality these Classe CAM 600 is spectacular sounding amp and run cool but big massive in size and very heavy. 
Dynamic headroom and bottom end extension and control are excellent.
The Classe CAM 600 excels in extracting musical details and nuances and information. The tonal is neutral and balanced across the entire spectrum with a touch of warmth. The noise floor is one of the quietest I’ve heard from any high end amplifiers. The amps are dead quiet and the music emerges from a dark black silent backgrounds.

These amps look very stylish too imo.
I happen to own these Classe CAM 600 monoblock amps in my dedicated home theater room driving my front speakers (B&W 800 D3). I have also tried the amps for playing music and they sounded fantastic for both stereo music and high end home theater setup.

One time I dragged these Classe CAM 600 monoblock amps to my dedicated stereo setup in a separate dedicated listening room and pair them up with my Magico M6 speakers that I have in there and sounded wonderful. I compared them with my Dan D’Agostino Momentum M400 monoblock amps (2 pairs) that I normally have in my dedicated stereo setup and while my D’Agostino Momentum M400 edges out the Classe CAM 600 but the Classe CAM 600 are bargain considering the price difference between these two amps.
My Dan D’Agostino Momentum M400 monoblock amps retail for $65k/pair and I have 2 pairs bi-amping the Magico M6 speakers. And I’m using the Audio Research Reference 10 linestage preamp and a complete full DCS Vivaldi stacks (Vivaldi master clock, Vivaldi upsampler, Vivaldi DAC, Vivaldi CD/SACD transport) as my digital front end source components. Even when I slipped the Classe CAM 600 amps in my high end reference two-channel setup the Classe simply performed wonderfully driving my $176k/pair Magico M6 speakers.

You should also consider other options such as the Audio Research Ref monoblock amps, CH Precision, Soulution, Audionet Max monoblock amps, Tidal, MBL monoblock amps, Burmeister, T&A, Gamut, Virus Audio, Constellation Audio, Halcro, higher end Naim separates eg Naim NAP 500 DR amp + Naim NAC 552 preamp + various Naim streamers + DAC separates. You will probably love how Naim gears sound. Even their lower end series or entry level series sounded very musical.

Oh finally I forgot to mention about Devialet gears. I highly recommend any Devialet. If you go this route you won’t need your PS Audio BHK Sig preamp and Direct Stream DAC. Devialet is basically all in one solution (streamer/DAC + pre + amp). Fantastic products. It starts at around $10k plus for the Expert 130 Pro to around $40k for the Expert 1000 Pro.
I happen to own the the Devialet Expert 440 Pro, which is right below the 1000 Pro for my master bedroom setup paired with the Wilson Audio Duette ll stand mount speakers.

One last thing I would like to recommend to you is the new Linn Klimax DS with Katalyst DAC architecture with its Linn Klimax Solo Chakra 500 monoblock amps. But this setup will cost you around $55k. $30k for the new Klimax DS (with Katalyst DAC architecture) and another $25k for the Klimax Chakra Solo 500 monoblock amps. With this setup you wouldn’t need the PS Audio Direct Stream DAC nor the PS Audio BHK Sig preamp.
The new Linn Klimax DS (with Katalyst DAC architecture) will blow away the PS Audio Direct Stream DAC. They are in different league. The Linn Klimax DS has built-in volume control (preamp) so the signal path is made as direct and short as possible. The new Linn Klimax DS (with Katalyst DAC architecture) is the best sounding digital streamer/DAC I’ve heard for under $50k. You will literally have to step up to MSB Select Two DAC ($150k) or DCS Vivaldi full four separate stacks ($125k) like the ones I have, or the Esoteric Grandioso full separate stacks ($100k+) in order to outperform the new Linn Klimax DS with Katalyst DAC architecture which retails for only $30k. This is a single box solution for you : digital streamer/DAC/preamp in a single chassis.

Hope this helps. Do not hesitate to ask any questions.