I have a K30 G4 and an EX. To my ears the G4 upgrade was worth the money, especially the usb upgrade. I use the server in the K30 to direct stream to my EX (not upgraded). This is where the EX shines. I had the EX as a standalone system for a couple years before moving to the K30. I found it good for a smaller roon library/player but the sound improved when going squeeze/squeeze or MPD.
Why do I have a player in the K30 and the EX? The K30 player goes through an mscaler for streaming and EX is fed upscaled pggb files.
I think if you can add a CX to the EX you will have a system that rivals a pre G4 upgraded K30.
The EX by itself is still a very good sounding system.