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
mahler123
On your MacBook, under System Preferences, Security & Privacy, General, check the settings under: Allow apps downloaded from... 

On my Macs it is set to "Mac app store and identified developers"

Updating the OS to El Capitan shouldn't have changed your previous setting but one can't be sure what may have happened in the interim.

Consider buying/using the AIFF file format for your downloads. Yes, the files are larger but require no conversion to be compatible with Mac (iTunes, right?) The cost of hard disk space has gotten relatively low. Now I buy and/or rip to AIFF in order to have maximum compatibility with present and future players. 

mahler123, when you get the message "unk developer" press the CONTROL key and try again.

Ok we are going to the Mac store today as my wife is disgusted with the performance of her 8 year old MabBook Pro since loading El Capitan.  I will ask the people there, though the drop off in Quality of the in store help over the past several years has been painful

Ok, both changing the preferences and and pressing the control key worked.  The problem now is that neither program shows up in my application file.  I downloaded XLD again, since it's free, but it isn't as it formerly did.  Now when I drag a FLAC file to the XLD icon the file Boyce's back to it's own folder.   
  Decibel wants to charge me again, and I had bought a 'lifetime '
subscription for $50 before so I didn't to use it.
  I have an Oppo 105 in the system which I use for audio only.  I bought a monitor and now I'm using the Oppo USB input to play the files.