You can pick up a Bluesound Node 2 2nd hand for 200-300 £ or a Teufel Connector 2 new for £110. Both have well regarded control apps & have RCA out. You can connect USB hard drives to both.
I don't, was bidding on 1 on ebay a week or so ago but lost out. I don't need it but have heard a lot of good things about them so thought would give it a go if could get for a reasonable price.