Hi Denis,
I stumbled across an old DSP plug-in on the WinampHeritage website that should let me replace the Stereo Tool DSP plug-in I have been using. So far it runs without issues with WACUP. It is called iZotope Ozone Free. You will need to run it's installer as an Administrator, if WACUP is installed under the Program Files (x86) folder. Before Stereo Tool, I used Ozone for years until iZotope discontinued it. iZotope Ozone Free is a full featured demo of Ozone that only runs 10 of it's built-in presets. I'm happy with the adjustments 3 of these presets make to the sound of my files. I'm pretty sure you will find 1 or more you will also be happy with.
This version of Ozone uses substantially less computer resources than Stereo Tool and introduces significantly less latency into the audio processing chain. This demo doesn't save it's selected configuration between WACUP sessions, but it's setup is simple and quick. Select the desired preset, then the plus or minus input level from the input plug-in being used, and finally the plus or minus output level to the output plug-in being used. I suggest you set the input and output levels so that what is shown on the vu meters do not constantly stay at their red levels.
iZotope Ozone Free uses 3 modules (valve equalizer, room simulation and tube amplifier) to perform its magic. You can look at how the selected preset has setup each module, but you can't change these settings. You can disable any or all of these modules to hear the affect they have on the sound. Depending on the WACUP skin being used it may be necessary to minimize iZotope Ozone Free's configuration user interface to keep it's vu meters (and other active elements) from interfering with (slowing down) the active elements in the skin.
Another benefit of using iZotope Ozone Free instead of Stereo Tool is the rate of WACUP's working set memory increase is much slower, even with the reported resource leak in recent beta releases. I use the WACUP option to recover working set memory that is no longer being actively used. It is set to trigger every 15 minutes. With Stereo Tool, the reported amount of working set memory would exceed 100 MB between these reset intervals on my computer. With iZotope Ozone Free, the working set memory has stayed below 80 MB between the reset intervals.