My next investment should be.....???

I am enjoying the following: McCormack DNA 0.5, Manley Jumbo Shrimp, KEF 104/2 (reconed - crossover stock), Cambridge Auzer 851N - Spotify Premium. Listen to Jazz, Female Vocals & Led Zeppelin occasionally. Room acoustics are not a point of debate for me (wife). I would appreciate any thoughts on taking this all to the next level - no budget in mind. My thoughts are to send amp to SMC for upgrade or buy same. Thank you for any thoughts. 
My experience has been that the least expensive and possibly greatest improvement you cold make would be to switch from Spotify Premium to Amazon Music HD. I made that switch and the improvement from Spotify Premium's 320 kbps stream to the Amazon Music HD rate of 850 kbps to 3730 kbps for Ultra HD is sometimes quite dramatic, depending on the recording. Your gear is all high quality and while you might be able to make an improvement with upgrades it would be costly.