How to make sound less detailed with warmth?

cables cables cables....

Ditch the Thiels - they are famous for your complaints and changing upstream equipment won't change anything that much (but you can get rid of some of the brightness by buying very high quality amps, preamps, and sources. Go that way and when you really get tired of them you will have some electronics that will sound worth while on your replacement of the Thiels with a more neurtal or warmish toned speaker. Been there, done that with CS3.5's. Loved them at the dealers and bought them, loved them even more when I sold them several years later after getting 2 new amps, a pre-amp and a source or two. Bought some panels and never looked back. Had beautiful natural Rosewood cabinets though! Even my wife liked them.

Ohhhh....come on....CABLES ??????

It might be a good time to replace your amp.
(many to choose from.....would you like some recommendations????)

Have you ever tried room treatments ???? (it could be the answer to your problems.)

Take out your 1.5" thick butcher block cutting board from the kitchen and put it under your rotel CD player and also try one under your preamp. If your components are on MDF, I found that it sucks the life out your components when damping.

You could also change out the tubes in your sonic frontiers preamp to warm things up.

You might see about getting an estimate to fix the B&K as I spent $160 repairing my Carver amp which was only worth $140... and I regretted spending the money since I could have sold it by stating "Broken Carver" and someone would have spent 20-40 for it to use it as a project or fix it themselves.

Get some Cardas Cross or Golden Cross cables.