Options to improve digital sound

Hi,

I am looking for some, hopefully, simple advice.  My current digital system is an M4 MacMini feeding a Holo May DAC into a PrimaLuna 400 preamp and amp.  My speakers are Devore Gibbon X.  I primarily listen to downloaded and ripped files with Roon and Audirvana.  I also use Qobuz, but not as often.

The sound quality is good, but I feel like it could be improved.  The options I'm considering are a Small Green Computer SonicTransporter i7 to replace the Mini, or a SGC UltraRendu to put between the Mini and the Holo May.

Which option would be better?  Is there a better option?  I'd like to keep the cost under around $2500.

Thanks