If you've got LTE you actually need far less local storage? My music library is close to 1TB and it's all as good as stored on my 32GB Nexus 5. I run an FTP on my NAS -- or if you don't have a NAS most half-decent routers support FTP access to a USB attached HDD -- forward port 21 from WAN (my ISP provides me a static IP / hostname but you can use a free DynDNS/No-IP for convenience), and I can download whatever music I want straight to my phone with ES File Explorer wherever I am. On LTE I get around 2MB/s while on a moving train. WiFi over WAN I can hit 5MB/s+
Another advantage is never needing to plug my phone into my PC to transfer music. Forget microSD and paying extortionate prices for additional internal flash storage - private cloud is the future