New Class A/B under $6K, your recommendation?

Okay I'm tiring of my class D amps and have upgradeitis. I want to try a latest greatest Class A/B amp - I'm thinking Benchmark AHB2, or Son of Ampzilla, or?
 I can drive it with a Manley 300B pre, or a Wyred 4 Sound pre, or directly from my Benchmark DAC into big BG Radia 600 speakers that are rated up to 400 watts. They are line array types using BG planar magnetic drivers - intended for wall mounting, but after hearing them and speaking with a BG engineer, I built beautiful boxes for them according to specs and have been grinning ever since.
 I spoke with Rory from Benchmark and he suggested that 1 amp - even though rated at 100 watts per channel would suffice. I could always order a second and use them bridged and be at the upper end of my budget.
 Any thoughts on what else I should be looking at? I'm looking for: Imaging, space, neutral sound (not cold, not lush and warm) - I can color with my pre if I should so desire. Thanks for your input!!
Benchmark AHB2 has the best specs of anything I am aware of (lowest noise floor etc)

If you have not upgraded to Benchmark DAC3, I highly recommend it over the DAC2
I have the AHB2 and it is the best SS amp I've owned. You can believe the specs because these are a clear and open conduit for your source. I suggest a tube preamp. They can come off as a little clinical depending what you feed it.
Thanks for the input! A used AHB2 is a rare bird, which I believe says volumes - and it has great - the best specifications. But as we here all know too well, specs don't always translate to great sound to any particular individual's ears.
 For tubes I have the Manley, and love what it (and 300b tubes) can do. But it's not quiet, so you're ruining that quality of the AHB2. It's also not balanced  (not a lot of 300B preamps are - like maybe one of them?) and I wonder what the AHB2 loses going to single ended?
 Someone recommended I consider the ATI 6002, I admit I know nothing about that company or their products. They make Theta according to their site if I'm seeing that correctly?
2nd hand Audio Research Reference 110 would be on my radar... about $4500 - $5500.  Or if you get lucky, you may see a Reference 150 used for close to $6k.
Try McCormack DNAS-750 mono blocks ,
I've seen used ones for $4,000.
I'm using the DNA-250 stereo and hope someday to upgrade 
to the &750s.

I’ve been very happy with my Spread Spectrum Technologies Son of Ampzilla Mk2. I recently bought a Pass XA30.8 to ’replace’ it, but the SoA holds it own.

At your budget range, you can step up to the SST Ampzilla 2000 Mk2 used or very close to the upper end of your budget new. You should have a really good chunk of your budget left over should you go with the SoA used.

These amps are true ’sleepers’ in terms of performance and value. They are exceptionally well reviewed.

PM me if you’d like more specific details...and no, I’m not trying to unload the’s a keeper. : )
Magnus Audio 400.
There are a couple of tubed monoblocks that would fit into your price range:

Coincident Technology Dragon 211 Mkii - tube compliment is EM7×1, 300B×1, 211×2 per Channel

Blue Circle BC2000 - they use a single 6SN7 tube. This one is in Canada and is selling for US$5,500.

Both output 75 W, which is more than enough ’oomph’ to power your speakers.
Magnus audio is out of my price range, but looks like a very nice amp.

Tubes- I already have a Rogue Zeus, I'm looking to have a SS amp that I can just fire up and forget about. I love tubes, but they really aren't ACCURATE (measurements- wise)and that's what I'm going for. Whether "accurate" sounds better to me or not remains to be discovered! 
There’s a new Magnus MA-400 for sale on Ebay for $5500. Joe, JMSound, is a great guy to do business with. There are several Audiogoners who love their Magnus MA-300’s.

I've had two amps in my system that do exactly what you're looking for although being very different in approach.  They are the Rogue Medusa and the Liberty Audio B2B-100 (of PBN design).  The Rogue is a class-D amp with a tubed input stage while the Liberty is a more traditional class A/B design.  Both are the epitome of transparency with amazingly clear and vivid 3D soundstaging -- significantly bettering amps from the likes of Bryston and a Class A-modded McCormack in this regard.  The Rogue has the benefit of being able to fiddle with input tubes to further tailor its sound to your system and tastes.  The Liberty counters with a high bias switch that adds a dose of fluidity, palpability, and dimensionality without sacrificing anything.  Both are extremely close in overall presentation, but in stock form I'd marginally choose the Liberty in high bias given what you're looking for.  But I know Rogue has recommendations for upgraded input tubes that could change things.  Really think you couldn't go wrong either way.  Hope this helps, and best of luck. 

 I have two power amps: I have the iconic Krell FPB 300cx 2.0 stereo amp for my mains and this new Anthrm 3 channel for my other 3 speakers. The Anthem 2 Channel amp is an impressive sounding amp. I LOVE my 3 channel  and it is in great company of course with my coveted Krell. 

But for around 5.5k prepared to be blown away by the 300w per channel A/B Bryston 4B3. I auditioned it last year and it sounded 90%?as good as my class A Krell sounds and that machine was 10K way back in year 2001! 
 Sorry, but I forgot to include the links!
I'm prepared to sell my Pathos Acoustics Inpol2 pure Class A Integrated amp for $3950. Mint with NOS Mullard input tubes/MOSFET output.  It is still Pathos' flagship integrated, $13K new, and in a totally different league than all the above . . . 
Absolutely love my AHB2 amps, loads of power, dynamic range, and amazingly transparent. They drive my Maggies with ease and are dead quiet. 

Onkyo M-5000R.  Except for some tube exotica you will not find a better looking Amplifier.  But wait - there's more!  This baby sounds better than it looks.  I have heard one and it has power and accuracy.  Strangely it is rated at 85 Watts but seems vastly more powerful.  It was much lauded by Hi-Fi Choice magazine.
I own the AHB2, which last year replaced a Bryston B60 Integrated (circa 2012, that I liked because of its neutral sound characteristics) in my system. I use it with a pair of Joseph Audio Pulsars, and I am enjoying it very much as my go-to amp - it has no issues driving them beyond any level I'd be comfortable with, and they are rated for 325 wpc if I recall correctly. The most amazing thing I notice about the amp is the speed and detail in the low-mid range, which completely embarrassed the Bryston driving both the Pulsars and an easier-to-drive pair of PSB Imagine B's that I own.

I use an Anedio DAC2 as the source almost exclusively, but my next purchase will likely be the Benchmark DAC3. Putting any kind of pre-amp in between the two was detrimental in my experience. But the overall sound is better than anything I've.heard in its rough price range.

You will no doubt have noticed that Benchmark will let you audition the amp for 30 days. I let it break in for about 24 hours and then gave it a listen. After that, there was no question of sending it back, and the Bryston was soon listed and sold. I suspect you'll be very happy with it as well.  Good luck!
Odyssey Audio Stratos Mono Extreme - $3400/pr.  That's what I'd buy for Class A/B under $6K.