@Beology
If you're thinking of buying BL5s and using a Mac as a source, then here's what I'd suggest:
1) Your harddisk can store your CDs in the original format (just buy a large HD and connect it to your Mac. There are also computer independent servers that you can control without needing to have a Mac connected, but let's go with the Mac for now). You can also use the HD in your Mac, but if you're building a large library of uncompressed files, then you'll eventually want an independent server.
ADDING: Sometimes I'll play a CD from the Mac, but that tends to be noisy, so the Mac has to be in another room than the one I'm listening in. That's no problem with the Airport Express, though. I control the Mac through the WiFi.
2) The Mac will send the digital signal, uncompressed, to your Airport Express (AE). You may be aware of this, but the AE can deliver both an analog signal to the minijack connection and a TOSLINK optical digital out through the same minijack. (Requires a TOSLINK minijack connector).
3) Get a TOSLINK to S/PDIF converter. (There are various available, from cheap ones to pro-grade. Get a reliable one within your budget).
Connect your AE to the converter through the TOSLINK optical cable.
Sample converters: http://www.ramelectronics.net/html/audio_toslink_adapters.html#co2
4) Connect the S/PDIF OUT from the converter to the S/PDIF IN on one BL5 - daisy chain to the other speaker.
You're set.
You've now created an uninterrupted digital chain delivering what's on your source to the Digital-to-Analog converters of the BL5s. You can play a CD in your Mac, or go from the lossless or uncompressed file on your harddisk, having control through iTunes/Frontrow, to all your audio sources.
If you want to colour the sound just use the Equalizer in iTunes, or get a digital processor (software) for precise adjustments and effects. (Pick a cathedral, any cathedral, for that guitar concert, for instance).