I own both tubed DAC and preamp. Definitely a very synergistic combination. In my system especially since both are Audio Research. Absolutely nothing wrong combining different brands.
One thing I must comment on is the word “random”. I assume you did not really mean just combining two different brands randomly. But that research into the sound quality of each… and particularly when buying the second is a part of your process.
I definitely do recommend both. Quite honestly when I added my tube DAC… it was astonishing how much more musical and realistic my system got.