System assessment...

lol! Yes, a good pet can definitely add warmth to your system.  And re DSP, I also am not a huge fan of adding (more) digital processing to one’s system if one can avoid it.  Another obvious way to add warmth to your system is thru your speaker choice.  I believe your KEF’s are known to be very detailed speakers.  A different approach would be something like a nice pair of Harbeths - they always make me smile.

dsp is very frustrating to work with initially. The interfaces are horrifying to deal with. But if you think about what happens along curve if there are low spots or high spots that may tend to distort the overall signal, correcting these areas could add a lot of Sonic improvement. My home theater system when I do DSP really helps to energize what I'm listening to.  

If you visit Chicago hit Promusica and Holms Audio. 

I would try acoustic room treatments first.  Even if you end up upgrading equipment, this will be helpful.  It's probably the most inexpensive route as well.  I found by adding absorption and diffraction in my rooms the sometimes shrill sounds I was hearing was improved. Rugs are easy.  First reflection points and ceiling absorption helped me.  Congrats on retirement!

Since you already have a good quality set of components, and are looking for the warmth of tubes without replacing major components, (and cost) you may consider ModWright’s Analog Bridge. I highly recommend it! Find out more here: 

https://www.modwright.com/products/analog-bridge/