Excellent Solid State or Hybrid Monoblocks Recommendations

@tweak1  I do have a modded Voyager GAN.  It is a very fine amplifier.  Not as good to my ears as my modded JC1 monoblocks but mighty fine.  I like having a menu of amps to rotate or have as backups.  Never used any of the contact enhancers - might give them a try.

I own a pair of BHK mono blocks. They are hybrids because they have a tube input stage.  They drive PS Audio FR-20 speakers.  Great amps. 

I am also a fan of the BHK 300 mono blocks.  I have used them with Tekton Moabs, Magnepan 3.7s and now Magnepan 20.7i's.  I heard a friend's 3.7i's being driven by a D'agostino S300 amp and even though his room wasn't very good his 3.7s sounded a lot better than mine ever did.  That led me to consider getting a high powered amp and used BHK 300's were the first ones that came up at a price I could afford.  They transformed the 3.7s which finally managed to outperform my Moabs which I still have and love.  What surprised me is the BHK 300's sounded better with the Moabs than my Aric Audio Super 300B SET amp with KR Balloon 300Bs and the Moabs sounded REALLY good with that 300B amp.  Getting the 20.7i's was another big upgrade to the system.  I had also tried the PS Audio M700's but I didn't really like those.  I think the BHK 300's at used prices are a genuine value and a great performer.

A Neurochrome 365 or a Purifi EIGENTAKT Class D Amplifier are both able to be produced as a Monoblock.

I know the 365 and the lower powered versions down to the 65 very well, to the point, I do believe the 65 might be my last owned Amp' when I come away from the present system.

I also know an owner of the 365 with a few Mod's incorporated who has been recently familiarised with a Purifi EIGENTAKT, the result being they are very impressed and are now building their own one with a few mod's learnt from an Amp builder/measurement group.

These can be housed in an very nice aesthetically pleasing enclosure and might require an EE's assistance.

I would bet all in any of these Amp's would come in at $2.5K max to build as Monoblocks.

In relation to the Commercial World of Retail Pricing, the BOM for these Amp' Types alone, if attached to a retail product, would put Amp's being supplied retail into the $20K - $40K zone, especially if a very fancy aesthetic was also part of the pricing for the upper end in the suggested price range.

The first Time I heard a Neurochrome Amp' it was on a £200K+ System, where the Soulution Power Amp' at approx' £50k was in use for approx' 2 Hours as the base Amp' used for Phonostage Demonstrations.

The Soulution was swapped out and replaced by the Neurochrome. For the 3-4 Tracks allowed for the Demonstration, the Neurochrome did not show any signs of having a Amp' immediately available to be put back to use, that could show it to be a underperformer, even though it did have a slight variation to how it delivers the end sound.  

On the same occasion following the Neurochrome, an individual known to have very adept EE Skills and has produced very attractive audio demonstrations, put into the system, their £400 purchase, that was a 4 Box Class D Monoblock imported from China. The builder had spent approx' £100 doing their own design hooks for the schematic/topology.

The system owner who also has a audio retail business claimed he might as well throw in the towel.

The Chinese Import was not as good as either of the previous Amp's, but if an individual was able to receive a Demo; of the Import Amp' and the Soulution, it would be some sales person that convinces a person to spend the extra £49500 on the Soulution Amp'.

In relation to the Neurochrome vs Soulution, the individual in the Demo' would need to be a Soulution die hard fanboy, to decide the Soulution was the one to spend the extra £47500 on to take it home.

In no way am I knocking Soulution Amp's, I have as an estimate heard them in use in the same system, for near 20 Hours of play time. I would be very very Happy to use one.

Have there been many changes to the PS Audio BHK 300 monoblock amplifiers over the past few years?

@jaymark Seems like there were some revisions that affected early units.  In case you're interested, PS Audio has a good forum where you can even find old posts from BHK himself.  Here's the thread about revisions:

PS Audio Forum: How To Tell If You Have The Latest Version Of BHK Signature 250, 300 or Preamp???

Do PS Audio BHK 300 monoblock amps require a 20 amp line?  If not require one would the sound better with one? Or is a 15 amp line sufficient?

15amps should be okay, but 20amps would likely be preferable if you're running off of a single circuit.  I run through a few conditioners and the Furman SPR-20i averages ~2 amps for the BHK 250 at moderate listening levels.  I'm assuming with all equipment powered and running BHK 300s, you could be pushing ~10 amps continuous draw for everything, but, for reference, the BHK 250/300 uses 10 amp fuses so you'd never surpass 10 amps per amp even at full throttle.