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.
