Looking for more tricked-out solution for iTunes

First- Love this receiver! Had it more than a couple years now.
Need suggestions on a good way to get the best sound from my ITunes library playing through this receiver. Right now, I picked up a used Gen 1 Apple TV and have it hooked up. Have a cheap monitor to access menu. I don't use this for TV, only audio.
The plusses: The unit has a hard drive and it has an analog RCA jack connection, so plug & play.
The minuses, no apps (like Pandora, etc.), limited features. Unit is old and getting a little cranky. Not sure this device is giving me the best sound, although it's not bad.
The new Apple TVs are streaming only, and USB or HDMI only. I believe the USB port on the 2150 is non-functional. (please correct me if I'm wrong), so conversion equipment (analog converters, etc) will probably be needed. Would love a push in the right direction on this.
I also picked up your new Bluetooth device, but getting choppy sound (bad wifi) for some reason when I use my IPhone 6 to play Pandora
. Hard to isolate the trouble with this.

The USB connection is functional for digital input from a PC or other digital device with a USB output. That would likely be your best source.

Thanks!

Another option, if you're looking for an audio-only solution, would be Apple's AirPort Express which has a combined analog/digital output jack.
http://www.apple.com/shop/product/MC414LL/A/airport-express