Audio Research Ref 10 vs 40th Anniversary preamp


I was wondering what the difference in the sound between the Ref 10 and the 40th ? Not much wrote about that. I btw have the Ref 6 but never heard the 10 or the 40th. 
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Hello everyone and happy new year. I’m on a hunt for a new preamp. Changing things over from my hybrid AV/Stereo to strictly 2 channel. Trying to decide on the following:

CJ GAT2 
ARC ref 10
Dag Momentum

Found a dealer demo ref 10 unit with warranty.  One owner reported that Ref 10 is a bit aggressive esp in the treble and at it wasn’t musical. I’d love to get confirmation. 

The CJ GAT 2 has received rave reviews. Only drawback is that it has only RCA inputs.  Is this a deal breaker if your system is balanced. 
The Momentum has some operating issues with the tone control which can be fixed($). 
Rest of my system

focal utopia evo
pacific bal dac
sonore signature/SGC Nas
krell 403 E amp (to be upgraded to monos)
You have selected my 3 favorite preamps. 
 I must disagree with anyone who would say that the Ref 10 is aggressive in the treble or not musical. I find the treble to be spot on. ARC tends to make a large wide and presentation from a front row perspective. This presentation tends to be dramatic (but not inaccurate)-- sort of like technicolor. To me, it is very alluring.
CJ is very true to life, sweet with a mid row presentation and a bit less slam than ARC.
 The DAG is among the best solid state preamplifiers on the market and will be more transparent than either of the tube preamps, but with less liquidity or, for want of a better phrase--je ne sais quoi.
Take what I say with a grain of salt because anyone who favors pure solid state will go with the DAG. But I am also a fan of a tubed pre with a ss amp  If you want to run balanced interconnects, the CJ is a no go as it only uses single ended to my understanding.
Hope this helps.
My vote is for the Audio Research Reference 10 preamp which works extremely well with any solid state power amplifiers (the best of both world)...I have personally compared all three preamplifiers in my system and ended up with the Audio Research.  The Ref 10 is the end game preamplifier...and it is so much fun to own especially when you could roll some tubes and get a different taste!
Ref 10 for sure.  Have 1300 hours on mine.  Its wonderful.  Never heard any aggressive treble.  Its very musical. My friend was listening to the system while I was testing tubes for his ARC vintage preamp.  Said was sweet airy, excellent depth and width.  He loved it.
New REF6SE is said to close the gap to the REF10 and might be worth a listen.