Mac into IRdac into Naim advice.

Hi all. 

I have  much of my music now stored on my iMac which feeds an arcam IRdac (via the usb feed) which then feeds my 282-hicap-150 neat motive 2's. My music files are apple loss less. Music generally sounds great. Just wondered if you guys had any thoughs on what your best set up given my kit would be. Can't afford to change anything atm!  

Thanks in advance.