I tend to agree with you on K.I.S.S. and the Vanatoo Transparent One powered speakers with built-in DAC sounds really intriguing for an office. I'm not sure how much space that the OP has for speakers and other gear but the Vanatoo look like they wouldn't eat up too much desk space.
I recently had a similar challenge that I only mention because I like using at least a small sub with bookshelf speakers. In my case the Onkyo TX-SR707 receiver driving my amazing little EMP E41-B desktop speakers finally died and I decided to use this as an opportunity to scale back the amount of "stuff" around my home office/gaming system. The EMPs are put away for now and replaced by powered studio monitors. I still wanted to use my Emotiva Ultra 12 subwoofer for deep bass and that left me with a problem. An AVR provides a good DAC and a good speaker to sub crossover - at the cost of buying an AVR and sacrificing shelf space. I drooled long and hard over Mayflower's
ARC gaming/music DAC (stereo RCA outs plus headphone-out and mic-in jacks) before rejecting it for a lack of a subwoofer-output/crossover. For now I'm using a low budget solution - powered studio monitors and a powered subwoofer connected by a low budget ($80)
Sound Blaster Omni 5.1 external DAC with a subwoofer-out with a crossover (Windows only). I'm sure that there is a more elegant solution for the OP and a better sounding 2.1/5.1 DAC out there but I couldn't seem to find one short of buying another receiver.