Direction on my next upgrade

I am a year into my journey down the audio rabbit hole. I am enjoying all the incremental gains and enduring the miss fires. My system is as follows:

Rogue Audio Sphinx V2
Fluance RT85 with Ortofon Blue
Epicure M150's completely rebuilt with kit from Hue at Human Speaker.

I am trying to figure out the next step on my journey. I am considering the next steps.

1- send the Rogue back to be upgraded to V3 which has a much better phono stage($500)
2- switch to a MM in the $500-$750 range
3- switch to a MC cartridge
4- add a seperate phono stage under $1500
5- add a subwoofer to the party

I want to pick the one option that will give me the most improvement for the money. 

Thank you in advance for weighing in with you knowledge and opinions.

Charles