can anyone recommend tube amp for dartzeel preamp?

I would ask Jonathan for his opinion if you have not already yet done so. I cannot respond directly to your question, but note that I have a darTZeel amp and a VAC Renaissance 70/70 Mk. III tube amp that I run with a solid-state, battery-powered Rowland Coherence II preamp. The VAC is a push/pull, 65 watts/channel, zero feedback triode design that autobiases and runs 300B output tubes (it also has a sentry circuit that shuts down any output tube that begins to go outside of safe operating parameters). It is all point-to-point wired, and features very high parts and output transformer quality (ten years ago, the Mk. III retailed for $14K and the Signature version $18K). Mk. III's can be had for between $3K to $4K used. I'm not necessarily advocating this amp - I have no experience running it with Evolution Acoustics speakers - but am simply trying to give you ideas. Again, I would talk to Jonathan if I were you.

with the level of quality of your dartz amp & pre-amp I doubt that a tube pre-amp at under $5000 or even $8000 would give you as much as satisfaction with your s/s dartz amp.
Even though one is s/s and the other is tube, the cheaper tube amp will not give you the same level of refinement as the dartz.
I have tried this route on numerous occasions & it always ends up disappointing. (always to the detriment of the cheaper component.)
Personally I would hold off to that purchase.
However if you would insist, i can highly recommend you give one of those tube lamm power amp a spin. Those have similar level of pedigree as your dartz amp.
Good luck.

I agree with everyone. I don't think you would be happy unless you get Lamm or current VAC amp.

I too was a solid state guy and now tubes. To me, like vinyl, tubes are away of life(music). Either you do it or you don't! Any half way attempt will just end in disaster("I tried tubes don't see the big deal" kind of talk)! Happy with dart? Stay the course. Looking for something else? Make the move(or another set up). I did. Not looking back! That is the way I see anyway.

Jwm:

The only "current VAC amp" that is point-to-point wired is the Statement 450. I remain skeptical that it is, overall, equal to or better than the Renaissance vintage of amps. It does not appear to be a triode circuit and it is not biased fully Class A. It's also a high-powered design (i.e., loss of transparency and delicacy) that almost certainly uses feedback (disaster), and the output tubes are pentodes. The Kevin Carter-designed Renaissance amps were all-out efforts from the late 90's, when the company was flush with cash from the great economy and its contract to make the Marantz Model 7 /8B /9 reissues. VAC is still a great tube gear manufacturer and it stands behind what it makes, but those days are gone, I'm afraid.