So damn hard deciding which tube preamp to buy!

Have you compared the Cayin to every preamp? There is always something better.

I made a  experiement witha   Jadis clone, 12AT7, with Mundorf caps, vs a  Jadis 20 yr old DPL, Mundorf Caps, Takman Resistors Reys.
Sure Jadis has the  finest power caps, Philips the blue ones, but really the improvement was only **miniscule**.
To me a  amp = amp\
DAC = DAC
Line Stage = line stage.
Minisclue gains here N there, Now as for 
Speakers = speakers
HUge gaps there. Each will sound completely totally differebnt from the next. 
Spaekers are everything, the rest is only minisclue gains. 
Speakers 90%++ of  the sound ina  system
the other less than 10% is split between 
DAC/CDP /Line Stage/ Amplificatrion. 

I'll bet that this Cayin sounds pretty good.
cayin sc 10 | eBay

Again, balanced or single-ended?

Bal and single ended, prefer balanced.

preamps are 20% of sound impact, very important.