I have an iMac that use to house my library but now is simply my general purpose computer, a Mac Mini which is my music server, an iPad with the Remote app and an iPod. My general computer use is fairly routine and with the Mac Mini and iPad combo I don't know if I have a need for and probably would not replace the iMac.
I love the Mac Mini in my audio system.
(2) Lacie Quadra2 HDD>(2) Cardas Clear USB Cables>Mac Mini (AIFF-iTunes-Pure Music)>Cardas Clear USB cable>Bel Canto DAC 1.5>Cardas Clear Light XLR interconnects>Bel Canto 500S amp>Cardas Clear Sky Speaker cables>Dynaudio Chorus 220 MKII speakers