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

You should be able to get a used Luxman C-900 U for this price.  I don't think you'll beat it with any other SS pre-amp in this pricerange.  Absolutely great piece of gear.
Why not move up the Esoteric line-Several Esoteric C-02x just sold on this sight for less than you want to spend
Tdimier— do you own the Luxman? If so how did you choose it?

68pete:  I would love a C-02x but my post is partially out of my failure to be able to find a C-02 (not even a C-02x) for under 10k.  One sold here recently that was reduced to 10k and sold quickly. 
Pass Labs Xp-22.  Silent and beautiful.
KARL-- good call   In my price range and is the type of unit I am looking for.  Funny I considered buying  an XP-20 years ago but a dealer had the C=03 that was so luxurious, I bought it instead..  
Have you tried looking for a Krell Illusion or a Krell Phantom 1 preamp?  Since you're looking for a "transparent" preamp, those are likely very good candidates and I would say that the Krell preamps are in the same "voicing" as the Esoteric stuff.  The Pass Labs and the Luxman are also very excellent devices, but they do have that FET coloration and warmth added.  Maybe not quite as transparent as the Krell/Esoteric.
The XP-22 is a two unit piece which you mentioned would not be preferable.  But, I feel like Pass really knocked one out of the park with this update of the Xp-20.  In my system it replaced an Xp-10.  I hear improved clarity (resolution without glare or fatigue) and more holographic imaging compared to the Xp-10.  I imagine it would do similar things in your system.  If interested, there is a nice thread on the Pass section of the What’s Best forum.
Thanks Karl.  I can do a two box unit but an XP-30 or 32 when it arrives would not be possible.

Auxinput:  TBH, I have never heard a Krell preamp. What you say makes sense, I just have no experience with them.

Actually, I think the Pass preamps that I have heard have less of the FET effect than the Pass amps.  I prefer bipolar transistor amps for that reason.
How about the Merrill Christine pre? Have heard it in a friends system and this review was spot on:
There’s one FS on Agon at below your budget, something to consider. (Not affiliated with seller in any way)
You can't go wrong with a Pass Preamp but why not an ARC? The LS 28 is an excellent unit and right in your price range unless you want to shoot for a used Ref 6. You have their Phono amp after all. I love your tonearm. Brilliant design. How do you Like it? The Anna is almost Koetsu stiff. If you have not already you should check you resonance frequency with a test record. Adding some weight getting both lateral and vertical frequencies just below 10 Hz will really add some kick to your bass.
Have you considered trying a high end passive unit ( could experiment with a cheapy first ). I did, and cannot go back. But, this is me, and my own experience.
You could be right on the Pass preamp voicing.  Every single time I have seen or heard a Pass Labs preamp, it's been attached to a Pass Labs amp, so I have not been able to get a good handle on the actual voicing.
Was thinking you might benefit from being able to use Krell's current mode and cast system if you get a Krell preamp.  Since you're looking for a single box, here's an Evolution 222 available now...  but there are some Evo 202s available too.  Then again, there's also this special situation on an $18k Krell Illusion preamp...

Also, here's a nice Vitus pre that retailed for over $14k in your price range.

Best of luck!
Krell 302e input impedance is tube preamp friendly, why not open to tube preamps?
Thanks for the truly helpful and interesting responses:  Here are mine.

Joecasey:  In my experience starting about ten years ago, I have preferred to have one solid state preamp or phono preamp and one tube preamp or phono preamp, but not two of one kind.  To my ears, it provides the best balance of sound without leaning one way or another.  Since my phono pre is the Audio Research, I thought replacing my solid state preamp was the right way to go.  On the other hand, because the sound of tube and solid state equipment has become more alike, my view could be outdated.

Soix:  Thought about the advantages of CAST, but I connect my preamp to the power amp with a 16 foot interconnect. Not sure what a CAST that long will cost, but I suspect plenty. Will ping Krell today.

RSF507:  I have read the reviews of the Merrill Christine.  It sounds very close to what I want.  Plus the unit for sale is not that far from where I live.  Seriously considering it and the XP-22 both of which can be had for under mid $6000's..   

MR Decibel:  I have no experience or knowledge about passive units.  I have enough to consider already and thanks for your response.
Update:  Soix:  I called Krell and I can get a 16 foot CAST IC for 1950, which opens up that avenue.There is an EVO 202 preamp up for sale--any thoughts?

Karl:  I am bringing home an XP-22 next week for audition.

 RSF507: I remain interested in the Merrill.  Thanks again.
There is going on simultaneous to this thread, I high end preamp thread.  One that is mentioned is an EMM Pre-2.  Have never heard it though.  There is a lot of support for the Ayre KXR preamp in that thread, but when I have heard it I found it too dry for my taste.
@teeshot -- just a couple general thoughts. If you really like the 302e you’re obviously going to build on that significantly with the 202. What stuck in my craw was a review I read by Wes Philips way back when Krell first introduced CAST. He used the amp and pre in normal mode and liked what he heard, but when he went into Current Mode he went all GaGa. I never forgot that, which is why I brought it up here, and I have to believe that advantage could help the 202 to be competitive with some other very good pres. Seems like synergy on steroids in a way. Last, seems like a heckuva deal on the 202. That’s all I got. Best of luck in whatever you choose.

BTW, just noticed there's someone selling 15.5' CAST cable on EBay.  Might be a lot cheaper...
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!!
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. 
fun thread and civil....nice
The Bakoon preamps sound superb.By far the best SS preamps I have heard.