Alternatives Software for iTunes on Mac


Been an iTunes user since its inception and quite satisfied with it with its overall sound quality in my system. Recently I have encountered some significant problems and have decided to look for an alternative to it. Have a large collection of music on a separate external hard drive in AIFF files, 2500 CDs or albums. Currently uses Apple airport express to wireless play music from my computer through a Rotes Integrated Amp and Monitor Audio Gold 100 speakers.  I am looking for a high quality software to replace iTunes. I must to able to easy transfer existing files to the new software. Any suggestion would be appreciated.
joscow
We tried Audirvana a while ago and after considerable listening on my 3 systems and my wife's system, we could not tell any significant difference with iTunes. This was only with our AIFF ripped CDs streamed wirelessly. We do not use any internet music services, so I cannot comment on them. 
Thanks to all of you for your comments and/or suggestions. Still have an excellent ear for good sounding music and will now evaluate your suggestions. Have been extremely happy with iTunes in my system where most of the music is AIFF topped CDs but the problems of the last six weeks have caused me to look for an alternative. I will certainly evaluate Audirvana after receiving so many recommendations of it. Thanks again.
Right on!  And you are using a DAC right?  I have a Dragon Fly Red and it makes a huge difference too!
another vote here for Jrivers media center..  Very configurable and able to handle large Library sizes with ease..