Depending on how good you are with computers, you can build a very cheap PC (and, if necessary, external drive) storage device, which you can output via something like iTunes (or any of its competitors) to a USB DAC to the receiver. Or an Apple TV via optical digital to the receiver. I've also been told that there IS a way to use the headphone out jack on a PC or iPod that doesn't totally kill quality and gives a full digital signal to the receiver... though I don't know how.

Then if your music is in an uncompressed format, you'll be all set.

For me, I overpaid to get a brand new AppleTV because I wanted the optical out and control via my iPhone. I think it cost me $400 total for it plus a 2TB external drive. I have to hack the AppleTV to make it read from that drive (though I can still stream my music from my computer with that drive to the AppleTV) before it's perfect, but it's working pretty well for $400. And like I said, I overpaid. I bet it can be done for much less.