For the money, the SP14 is a decent entry level Pre. I added some Mundorf SOG caps and some 181 treasures to mine as well as a third preout for a sub. Improved the sound but could never get the "hum" from appearing on my Cornwall III or Heresy III drivers. Played around with grounding etc to no avail.
Upgraded to a PrimaLuna Dialogue Premium preamp with the 12AU7 first stage and drivers. You can tube roll to your heart's content with that valve. Difference is night and day on sound quality and the noise floor is in the cellar now. PL is also bout 3x or so more $, so I guess you get what ya pay for.
VTA has been demoted to second string in my workroom system for now.