Excellent Solid State or Hybrid Monoblocks Recommendations

Have you looked into PS Audio's hybrid amps?  I have a BHK 250 that sounds excellent with Scansonic MB3.5s, which have similar requirements as your Aerial Acoustics.  The BHK 250 is on clearance now for ~$4k on PS Audio's site and a steal at its current price.  There were also a used pair of BHK 300s that sold in the $6k range recently, so may be worth keeping an eye out for if you're set on going the mono route.

The 6922 tube and its variants in the BHK 250 are fairly low maintenance, long-lasting and not too expensive unless you get into the rare and exotic tubes.  I've had great results upgrading to Acme's silver fuses and tube rolling.  I really like the ability to alter the amp's voicing, which may also appeal to you.

I might have been the one who bought those 300’s😄. So far I am really enjoying them.

@curiousjim 

Congrats!  Those were very tempting for the price. 

Which tubes are you currently running?  I found the 6DJ8 Amperex A frames (~$70/pr on eBay for NOS) to be a great reference tube.  They do everything well, excellent imaging and very balanced across all frequencies. Great place to start if you're running stock tubes, especially since they're easy to find as NOS and reasonably priced.

My current preferred pair is a set of Westinghouse 6DJ8 medical grade tubes (likely rebranded Mullards) that have more of a 'live' feel to them, which win out slightly over the Amperex.  I tried a lot of others ranging from Valvo to Russian NOS to BHK recommended Tungsram, but the Mullard and Amperex tubes sound best to me so far. 

For reference, the BHK 250 even manages to drive my MBL 101s at moderate listening levels.  Great amp with plenty of power for most speakers.

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.

many thanks.  I was going to pick up a pair of used PS Audio BHK 300 monoblocks used then got cold feet when the seller did not know how old they were and the serial numbers were non-sequential.  So I ordered a brand new pair from P SAudio and traded in one of my amps in my collection.   Glad to know I should be OK with 15a lines.

@jaymark Any time and congratulations!  Bascom King's designs are so well-regarded that you can't go wrong, especially since these ended up on many "best of" lists.

You may also enjoy the tube rolling threads on PS Audio's forums:  PS Audio - BHK 250 / 300 Tube Rolling Thread

Something really nice about the BHK amps is that they accept the 6922 variants without any special configuration.  Bascom replied on one of the PS Audio threads and recommended the Tungsram PCC88, but it's a very laid-back tube.  I went on a tube binge and have tried ~15-20 different sets, so let me know if you'd like any tube suggestions.  I also had a positive improvement from Acme's silver ceramic fuses, which were ~$130 per amp for the set of 6.

Hope to hear your impressions after you're able to set your new monoblocks up!

@jaymark I'm just dipping into the German tubes since there's such a price premium and the market is flooded with fakes, but the ones I've tried have sounded great.  Have you checked out Brent Jesse's stock?  For ~$100 more for the quad, he's got the Siemens Cca, which is supposed to be the top of the line Siemens tube.

My current favorite is Mullard's 6DJ8/ECC88.  If you enjoy acoustic performance, piano or vocals, they sound the closest to live music to me and very addictive.  There's a premium on the original Mullard branding, but generally can still find them for $100-150/pr for NOS and all sound very similar.  You can find some of the rebrands for under $100/pr. with Brent Jesse selling a top end E188CC/7308 version for $375/pr..  I've noticed I need to turn up the volume a bit more to get good solid bass with Mullards, but its mid-range is what sets it apart from other tubes. 

Tungsrams are on the soft side and opposite of the stock tubes that come with the BHKs.  They're worth having as a spare set, but (in my systems) make voices seem further back and bass response a bit too soft.  Not as soft as the Valvo E88CC I have, but definitely on the soft end.  As a cheap Russian NOS, the 7308/E188CC National branded Vokshod sounds very close to the big name European NOS and not a bad tube.

I'd highly suggest checking out Amperex 6DJ8 A frames as a reference point.  They're such a well-balanced tube and have been very helpful with testing equipment changes and diagnosing issues.  NOS are easy to find under ~$70/pr. and sound great with livelier music, even at lower volumes.  Strong across the whole range with great imaging, just not a standout in any specific area. These may be a good starting point where you can make decide how you'd like to tweak the sound or what may sound best with your equipment.

Generally, I've tried 6922, 6DJ8, ECC88, 7308 and PCC189 and prefer the 6DJ8/7308.  These smalls tubes really don't get too hot and the red light in back will go out ~10 minutes after you shut off the main power switch, so it's safe to switch out with a gloved hand.  I also noticed the Acme fuses narrowed the gap between tubes and improved bass response with the softest sets, but just my experience.

@jaymark How are you liking the BHK 300s compared to the JC1s so far?  Hope you were able to get a few good listening sessions in!

@jaymark Glad you're enjoying them!  I have an old A23, but haven't heard any of the newer John Curl designs.  It's a fine amp, but the BHK 250 is in another league.  Ironically, it also developed a random channel dropout issue once it warms up.