Honestly, I would stay away from the Cary SLP-05. It is a massive unit and too “tubey” sounding to the point that it loses the holography. It also doesn’t have a very low noise floor, which is very important for headphones.
My pics would be:
PS Audio BHK Preamp - can be had used for $3500 or less. Hybrid tube input stage. Fully balanced topology. Incredible imaging and tone across the board.
Audio Mirror Linea - this delivers a more liquid, organic and warm sound while still retaining a good amount of detail. In my opinion the best bang for the buck if you are truly looking for a barebones solution. It’s $3K new and only has three sets of single ended inputs and one set of outputs.
I’ve heard both units beat out other preamps exponentially more expensive than them.