dumb question, streaming music to a preamp?

Hi. I am trying to put together a low cost system for my daughter, who is sharing an appartment with a few friends. We have a Luxman L-480 integrated amp and some TMM floorstanding speakers I built from a kit. She has WiFi in her appartement. She would like to use Spotify, which claims CD quality and allows you to select play lists or albums from more than 5 million albums. So how to get the music to the Luxman amp? Could buy a Sonos unit, but that is $399, which is about 1/2 the cost of everything else so far. Do not want to use a phone as have data streaming limits. Do not want to use a dedicated computer or iPad as too expensive as well. Any ideas out there. Could stream from her computer, but it just can not be tethered to the Luxman amp with a RCA cord. And if stream from her computer over WiFi, what device picks it up and converts to analog for the Luxman? Thank you for your help. This area is changing really quickly, and I have never even thought about it before.