Seeking Suggestions on Preamp Upgrade (CJ, Aesthetix, EAR)

Make sure the impedance matches as suggested above by unsound, and weight your opinion about responses you receive toward those from users, as opposed to those that have not owned or used the equipment they are recommending or disparaging. 

My general opinion is that if I have not heard it I can't have a valid opinion on how it sounds.

David - there is a VAC Ren Signature on the A-Gon listing right now that would be perfect with your PASS and fit your budget easily as well.  Do NOT hesitate as this is a great pre at at great price (no affiliation, just a very happy VAC owner)

Unsound and jperry:

Thank you for the insight on the impendence matching between the source and load.  I read some on-line information on this topic.  It appears that the the 1 to 10 ratio is related to balance between the maximum power transfer and system power efficiency optimizationis.  Back to the actual impendence readings for each brand listed above, none of them can meet the requirement for the rule of thumb, c-j's output impendence is less than 500ohm, and barely 100ohm for ET5, interesting perspective.

thank you again.

Did you eliminate VTL's 2.5 and 5.5?  I've been very happy with the 2.5 for many years with a McCormack amp. Lush and non fatiguing.

Oh my, this question is a delight to which to respond.  I am a long time customer of Don Sachs who produces a 6SN7-based custom-made tube preamp in a beautiful wood cabinet.  By far, it is the finest preamp I have had in my 45 years of having good to great gear.  Don offers lots of options including a remote control, XLR connectors, caps upgrades from Mundorf Silver Oil, Jupiter Copper, to Dueland caps that increasingly enhance the performance of his preamp.  The basic preamp runs around $1800 and betters the performance of preamps many times the cost of his preamp.  Google "Don Sachs Consulting" for more information.  This is my highest recommendation for a preamp.