Best 3 tube preamps under $18000?

You absolutely have to consider BAT REX- it bettered some of the preamps, mentioned above, in my system, in terms of the SQ.
Speaking of functionality and flexibility, I cannot imagine anything better.

I own a REF3 and had a REF5 for demo and as per Kurt_tank posting(Note: The Ref. 3 is very close to the Ref. 5 sonically, and if bought used, it is a bargain, (@ $5K), IMHO.)

I agree with him, I did allot of research and decided to place an order for a VAC Signature MKIIa so this will be interesting.

I also have solid state amplification, mono blocks so when I was doing research a couple of areas were important to me;

1. True balance design
2. RCA and XLR connection, in my current set-up I use all XLR cables so the pce had to offer XLR outputs and inputs.

What are your IC connections?

There are some great choices above but because of my basic requirements many were eliminated, the Einstein MKII interested me but after more research just too many tubes, runs too hot and I personally don't have an appropriate spot for it.

What's the rest of your set-up, are you looking for line only or including phono, I ordered my VAC with phono.

Every amp mentioned here is worth auditioning, as is the Joule LA300, and if you don't have money burning quite as big a hole in your pocker, the Joule LA150 MKII SE. Not sure it has been mentioned yet, but no preamp survey is complete without listening to some of the CAT preamps.

Ooops, I should have mentioned the Joule LA 300 (and the brand new fully balanced Joule 450, which I heard @ RMAF this year and was formidable to say the least). I for one have never been impressed w the CATs. YMMV.

Not sure what SS amp you have in mind but you might want to try a Cary SLP05. Pretty flexible & you can add the phono stage for less than $18000.