My whole system practically. Twenty five years ago I stopped with Mark Levinson 20.6's and the 23.5, the CAT SL-1 preamp and the Theil 3.6's all wired up with MIT Reference cables. The only thing new is the digital front end (Aurender N100H and Schitt Yggy dac) as they are the only components that significantly improved digital playback in comparison to yesterday's state of the art transport/dac combos regardless of price. But for the rest of my system, over the last twenty five years I have not heard any amplification that would make me retire the Levisons and CAT nor any box speakers that are significantly better than the Thiels, with the exception of the Magico S5. But not for forty grand; maybe a used pair in the future.