With Apple lossless as a the compression codec, you are not losing quality at all as it's a lossless codec. AAC, MP3, etc. are lossy codecs and introduce compression artifacts given their nature unless you are encoding at extremely high bitrates, which lead to bloated files and would then give you no advantage over the raw AIFF.
Again, if you have a newer Mac computer, try the digital audio out and see how it compares.
My only point with the DAC aside was simply that some have said that there is a bandwidth limit on Toslink connections as opposed to digital RCA. Thus, (and I haven't tested this) there MAY be a difference in a top-quality analog feed vs. a Toslink connection.
I do everything digitally and haven't dealt with anything analog in years. Indeed, my Anthem has all it's audio connections to all sources digitally. So, given the fact that you are using some good McIntosh gear, you may find that your biggest bang for the buck is indeed going the speaker route... so a blind test may work best.
Again, if you have a newer Mac computer, try the digital audio out and see how it compares.
My only point with the DAC aside was simply that some have said that there is a bandwidth limit on Toslink connections as opposed to digital RCA. Thus, (and I haven't tested this) there MAY be a difference in a top-quality analog feed vs. a Toslink connection.
I do everything digitally and haven't dealt with anything analog in years. Indeed, my Anthem has all it's audio connections to all sources digitally. So, given the fact that you are using some good McIntosh gear, you may find that your biggest bang for the buck is indeed going the speaker route... so a blind test may work best.