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