transistor pre with the sound of tubes

I've got tube gear, so you definitely do not have to be mature! 

all kidding aside

i agree w others whom have suggested the schiit freya as a good first entry point for a tubey noobey to get a sense of what tubes can do... without breaking the bank... and easy to flip at minimal loss if unimpressed

Talk to Johnny Rutan at Audio Connection.

There's now an "enhanced" version of the Belles Aria preamp, and the Belles Virtuoso preamp may be, or may be soon, available.

Since you gave no system context you get suggestions that spread all over the place.  A tube preamp is not a challenge to own or use.  Dual triodes last a long time before degrading and they can offer superb sound quality even in quite affordable implementations, and are widely in circulation used.  If you want a no-hassle tube preamp look for a used Conrad-Johnson in your budget range, or a re-imagined PAS from Ehrhard or Vacuum Tube Audio, and enjoy!  If your pockets are deep enough, look at VTL.  

Barefoot sound Micromain 27
Nuprime EVO dac
Nuprime CDT 8 Pro
Various acoustic tuning