If it's feasible, you can boot your 21" iMac into
target disk mode, cable it up to your 27" iMac.....
The inability to run a cable to the 27" is the reason I kept the 21". When the 27" came out, Apple dropped the TRS audio cable input.
You misunderstood me.
My suggestion is to use the 21" iMac's audio input jack to import your music and to then transfer it to the 27" iMac with drag & drop by cabling the two iMacs via firewire.
That would avoid both the CD step and Bluetooth limitations.
Update: But one of the adaptors to which joemike linked is a better option.
