Preamp shopping for pass ACA monoblocks

Have two pass amp camp stereo amps (32wpc each) running as monoblocks with Tekton pendragons and I’m in the market for a good preamp. Have a cheap aiyima tube preamp presently. Any ideas or suggestions?

thank you!
What kind of mods did you do to the ACA's?
No mods, they are stereo bridged for mono use. Budget is not a lot more than $1000, less if i can make it happen.
I'd recommend the B1 buffer. If you're in need of gain in the pre-amp, that can be had with the Korg triode variant of the B1 or by adding a BAGS to the output of the buffer. I'm contemplating the B1 with a complimentary BAGS for my F5. It's the most neutral configuration to be had. The Korg triode configuration can be voiced to different distortion signatures by swapping resistors, which the kit comes with. The choices depend on how colored your ACA's are and whether you're looking for more color or not. 

The BAGS is the Burning Amp Gain Stage and they come in 3 varieties, complimentary, single ended, and differential. 
Is the b1 a diy build or can I buy a completed unit?  What about other preamps with a no gain stage? Schiit freya+ for example?
Akitika PR-101 preamp is fine and nice.
There are Pass built B1’s out there. It’s an obscenely simple circuit to build though. Nelson sells the boards and matched JFETs for $40 at The Schiit wouldn't be a bad option either. 
I built the Bottlehead Smash and use it with my Pass ACA monos. Nice match. Their 300B preamp is said to be even better. 
d2girls, Have you built the Akitika PR101? I built the first amp and was very happy with it, Ive been thinking of giving the preamp a try. 
Akitika GT-101 review