Qobuzz - Spotify

If your ok with current SQ just get a iPAD mini and dedicate it to your rig as a streamer and just use the Spotify and Qobuz apps as you do now. I think you can still buy iPAD touch online at Wal-Marts and the Amazons.  Are you going digital into the Marantz from the iphone?

Try some third-party tools such as AudFree Spotify Music Downloader to download and save Spotify music as MP3s so that you can play Spotify music more freely on the device you want.

As for me, Spotify is the best music streaming service. But I can't download and play music offline with its free account. Fortunately, now there are many Spotify Music Converter for Mac for all fans to download and convert Spotify to MP3, AAC, WAV, FLAC, M4A, M4B, etc at faster speed with lossless quality. 

A pre-owned Auralic Aries Femto with Linear Power Supply. Does everything you need and and has an excellent third party music app.

Just use a Google Chromecast Audio.
$40 on eBay brand new.
Control direct from iPhone.
Cheap but definitely not cheap sounding.

Bluesound Node 2i

I use a Squeezebox Touch and a dedicated PC running a Linux OS (Vortexbox) which uses Logitech Media Server (LMS) software to manage things. Work perfect for streaming Qobuz and also managing my own library of 60K tunes.

The SB Touch is out of production but are available used and there are a number of Raspberry Pi and other PC player options. LMS is available in versions for Windows, Apple and Linux so you have a great deal of flexibility in terms of PC hardware.

I've been very, very pleased with my setup. No urge to change it in any fashion.

Bluesound Nodes
Bob

$500 to $1K

I'll save the others from this response. What is your budget?