Adding a tube DAC to my BLUESOUND VAULT

I recently purchased a used BLUESOUND VAULT ( cd ripper and streamer) and after reading a lot of posts on various sites I may add a Tube DAC in the $500 or less price range to my setup  I have the VAULT hard wired via CAT 6 > RCA out to RCA INPUTS MFA MAGUS A2 tube preamplifier > MEITNER MTR101 MONOBLOCKS > BOZAK URBAN speakers. So, thank all in advance May I have some ideas and suggestions please?
Agentwja