Very interesting system - and subject! Congrats, I commend you on all of the time and research you must have put into this.
I have been resisting going for a hard drive based system just because of sound quality concerns and the tactile "Classic" feel of loading CDs or vinyl from a "Collection" but this is more and more starting to look like an option. A few questions if you have the time...
Do you buy some music from iTunes or just rip your CDs to your Mac Mini. I ask this because I wonder if the quality is the same? i.e are the file you buy from the iTune store lossless?
Also, most of the audiophile discussions I have seen regarding a Mac as system central use a Mac Mini. Is there any advantage to using the Mini vs. an iMac. Just seems that an iMac would give you the screen interface as well as a larger hard drive (although I realize this is negated by the external hard drives).
Next question is how does the iTunes interface with the music files that are stored on a different drive? I would presume that you must see the collection list/album artwork thru iTunes but then get the music files from the Drobo? I asked this question at the Apple store and they didn't really have an answer - said it could be done but would be slow.
Any other advice you have for a clueless "newbie" just starting to get into this realm? Thanks in advance for any input.