I know want an upgrade over rPi but If you want a cheaper option, you can buy an android box and install linux on it. most of them have unlocked bootloaders. you can usually find a ready to use .iso on Armbian community forums by searching the SOC model there.

personally I run a 5$ android box. it has a quad core cpu + 2GB of ram. I use it for hosting my music library on an external hdd and streaming 1080p video. I also set it as my vpn gateway. It’s enough for my use case so I didn’t upgrade it.