Get a MacBook Pro but load your music on a firewire-connected external hard drive. Buy Pure Music ($129) as your music player; it sits on top of iTunes and works with it so you can play high-rez FLAC files through Pure Music which you ordinarily can't do on a Mac. Buy a USB-DAC (so many options--I chose a North Star USB DAC32) and a good USB cable (I chose a Wireworld Silver Starlight USB for $250) to run from your MacBook Pro to the DAC. Hook your DAC up to your preamp and do all your playlist creating, music selecting, etc. on iTunes on your laptop. You can also use the Apple remote app on your iPhone or iPod Touch or iPad. I have been enjoying great sound and easy user interface with this setup.
Alternatively, you can buy a Squeezebox Touch, connect it to your preamp (its internal DAC is really good) and stream all your music to it, using your laptop (running the Squeezebox interface, Logitech Media Server) or iPhone/iPad etc. to select your music, playlists etc. The Touch can also be used with an external DAC via coaxial or Toslink cables, but try its own internal DAC first, you may find you don't need an external DAC. I find the Logitech software interface really easy and flexible to use, more so than iTunes, but YMMV.