FLAC On A Mac

I know this topic appears here often but it seems to change every time I try to do a download.
I have a 7 year old MacBook Pro that i recently changed to OS to El Capitan after endless badgering from Apple to do so.  I previously had both XLD and Decibel on my OS for converting FLAC to Mac Compatible formats for the few downloads that I had ordered from HD Tracks.  
  I hadn't listenedto these downloads since the afore mentioned conversion.  i just ordered a new download (24 bit) from Presto Clasical and now I am getting messages that both programs will not work because they are from unknown developers.  Why these developers have become strangers to Apple after happily coexisting with them is another story but can someone tell me what the current best program for playing these files is>  My Internet search is unhelpful as everything seems to be recommending these two programs