Solid State Preamp Under $8000


I generally buy a piece of equipment that has been out for about four years and keep it for about 5 to 6 years. In this manner I get the fun of buying a new (used) piece of equipment every year and not paying retail prices. 

I have had my Esoteric C-03 preamp for 5 years and am considering replacing it with a newer model.  I have liked this unit a lot.  It sounds great and is a joy to use.  Why replace it then?

Well if there is something out there used for $8000 or less used that will give even greater transparency than the C-03, I would be a buyer. In general, the voicing of my current set up seems spot on. 

 I would prefer a single box unit if at all possible because of limitations on rack space and interconnect length. I do not want to risk a lateral move at this level of investment.  

Any thoughts would be much appreciated.

Current System: 
Feickert Firebird/ Reed 3P/ Ortofon Anna
Audio Research Reference Phono 2 SE
Esoteric C-03
Krell Evolution 302e
TAD Evolution Ones
Esoteric X-03se




teeshot
I have heard several Krell preamps, KAV-280P, HTS 7.1, S1200U, Illusion II, Phantom I.  They are all excellent, but I would avoid the lower cost models as their power supply is typically undersized (i.e. KAV-280P, Phantom III).  In my opinion, there is a "magic" from the sound of Krell preamps that are not available in any other devices, but I do understand that they are not for everyone.  Since you are coming from an ultra-clear ultra-high-resolution Esoteric preamp, I would concur with soix's recommendations on Krell preamps.  I have even heard the Phantom I mated with an Evo402e amp - sounds awsome!!
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The 202/222 preamps can be had for cheap (they are basically previous generation to the Phantom series).  Excellent buys, but they are getting just a little bit old - can be 10-11 years old.  The Krell Illusion that soix mentioned for $8400 would be an absolutely awsome device, but it is over your budget (unless you want to stretch).  I think that's about as good as you can get.  And I will mention that I heard all Krell preamps using standard XLR cables (I never heard what CAST can do or if it sounds different at all).
I thought that this thread was very helpful to me, so I am writing a post script. I ended up purchasing the Merrill Christine preamp used.  Before  I purchased it from a very nice seller, I had the opportunity at a kindly dealer I work with to compare it in an all Audio Research system to a Ref 6 preamp.  In that system, I much preferred the tonality and spatial characteristics of the Christine.  For me, it may have been a case of too many  tubes with the Ref 6 and a tube phono preamp and amp.  I then got the Christine home and borrowed a Pass Xp-22 from another dealer and compared the two in my system.  The differences were not huge, but I preferred the Christine over the Pass unit in my system because the Merrill sounded more real and neutral to me (as in a touch less bright) but once again seemed so transparent with great imaging.  The Pass shaded the Merrill in dynamics, and it might be slightly more extended in the low end. The Pass is also more flexible with analogue and balanced inputs (Merrill is all balanced). Both are superb in my view, but you have to hear the Merrill to understand its excellence.  I would think you would have to spend a great deal more than this price level to get better sound.  
@teeshot nice comparison and glad you like the Christine. I'm very close to pulling the plug on one myself that's listed on the Asylum but have to sell something first.