PS AUDIO bhk pre-amp vs upper level reference pre-amps?

I would agree with everything verdantaudio said. The BHK pre sounds much better when used in balanced mode and the sound can be tailored quite a bit depending on the tubes one chooses to use. There's a lot of changes in sound characteristics between say a RCA 12au7 Cleartop and a Raytheon 7308. I've found either 60's Siemens or Telefunken 7dj8's to be my preference. There's a very long thread on tube rolling in the BHK pre over on PS Audio's own forums. I'd also mention that the new PS Audio Stellar P3 power conditioner improved the sound of the BHK preamp so much more than I expected I'd almost consider it a "must have" upgrade if one can afford it and you have the room. 

In your system, you might like the BHK.  I replaced an Ayre K-5xeMP with the BHK and it was a step up once I rolled in some NOS tubes.  I replaced the BHK with an Art Audio Conductor.  

Note:  The stock PSVanes are not ideal in the BHK.  I found it disappointing with the stock tubes.  Kevin Deal sells a set of NOS Tunsgrams that are spectacular with it.  

I kept all three for a stretch and did some ABC testing when I started distributing the Art Audio line of equipment.  

The BHK excels in a fully balanced system.  Whether it will be a better fit for yours is a matter of taste.  The advantage of the BHK is it is a bit more flexible in terms of Tube rolling.  I opted against an ARC preamp given the limited choice of 6H30s.  

The BHK will probably not be “better”.  You aren’t going to get improved resolution or a bigger soundstage anything of that sort.  But it may be close to a push vs. the ARC or it may have a more appealing sound profile at a fraction of the price and will allow you to go from two remotes to one.  

Incidentally, in systems that are not fully balanced, the BHK was a step down from the Art Audio.  With single ended amps the BHK is a bit disappointing but that seems to be the case with virtually every fully balanced unit I have heard.  They always seem to need to be fully balanced from source to output to get the most out of them.  

I'd be curious if anyone compared the BHK Pre to any McIntosh or Pass Labs Preamps

I have also Carver Raven 350.
I am interested in either Allnic Audio L-7000 or PS Audio BHK preamp. I am a big fan of 3 - dimensional, huge soundstage and holographic sound. So which one would be perfect for me and Carver Raven 350 amp.Thanks

I had the BHK preamp and only replaced it when I could afford an Allnic L7000 preamp. Despite the large difference in price, the BHK came quite close to the Allnic's performance. They were hooked to BHK 300 monos. Definitely give the BHK pre a listen.

The BHK preamp is a Stereophile Class A rated preamp. It’s a superb unit and I love it. I’ve owned the Ref 6 but could never warm up to it. I always felt the treble on the Ref 6 was a little aggressive and not as smooth as I felt it should sound. The synergy with the rest of your system should be wonderful and I personally would swap out preamps. 

The BHK is an absolutely great preamp for not a lot of money. Bascom King with Paul McGowan and everyone at PS Audio do an awesome job.