IMHO, the law of diminishing returns kicks in quickly trying to upgrade from the KEF R series. They already feature low distortion, low compression, relatively flat FR, and even directivity.
What makes up the rest of your system in your office?
In my office (also OG R3s), the source is my PC running
Dirac Standalone running into a Schitt Modius DAC running into a Peachtree Nova 300 integrated amp. The 'component' that makes all the difference is Dirac. My opinion is, keep what you have and improve with room correction and perhaps some modest treatment.
The ONLY reason I would consider upgrading is if I felt I could benefit from wider dispersion, which is antithetical to my office room dimensions.
In my home studio, I have Neumann KH120 II monitors. I find them to be a lateral move compared to the KEFs.
Here is the my measured in-room response of the R3s with and without Dirac correction. I don't feel like I need subs, because the R3's low distortion lets me get away with a little bass enhancement, which extends response down to ~32Hz in-room.
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