I Tunes to my System

"Though if you've downloaded music on to iTunes in lossless format that does change things..." +!

If you are talking about lossy iTunes files it's not worth investing much in. In this case a bluetooth receiver with RCA outs would be even simpler and you wouldn't need to put the laptop or desktop next to the preamp.

If you've got bitperfect lossless rips of CDs in your iTunes library then let everyone know your budget etc. and these other suggestions (i.e. PC auduio, dacs etc) will come into focus. Cheers,
Spencer

+1 Ghosthouse. I would think that with your system, using a DAC between your computer and your Pre would serve well.

Jl35 makes a good point in that the $$$ spent on hardware need not exceed that of the driving software and file type.

Timru's suggestion of the Mediabridge mini to RCA connector from headphone out is certainly easy. Not that much harder but possibly providing a step up in sound quality for not a lot of money would be to add something like an AudioQuest Dragonfly DAC on a USB port of your Laptop. USB>>AudioQuest Dragonfly DAC>>Mediabridge mini to RCAs IC>>Preamp. A low cost/high value product to consider using with the above is BitPerfect ($10?; software to run your iTunes music).

Though if you've downloaded music on to iTunes in lossless format that does change things...

Agree with above. iTunes is pretty low sound quality and really not worth the more complicated or expensive alternatives.

You may get lots of suggestions on this but the simplest is to get one of these and hook the headphone out from your laptop to a line input on your preamp. This would be akin to running the headphone out from an ipod in to the stereo.