About the silver colored variable slow turn on model, I missed that one due to being critically ill/totally disabled for several years. I wish I that I knew more about it. Moreover, I wish that WBL would make more Gatekeepers, especially the 4 outlet model, and if the newer model is a noise improvement, those too.
That said, I have six of the 4 connector WBL Gatekeepers, & each makes significantly noticeable improvements in the video quality of my televisions, in the heard audio quality of my 600watt mono block amps, in my 150 watt stereo amp, and in my electrostatic speakers. I use separate units for switching supply supply gear.
I wish that I had purchased more, since I have not been able to find one since my purchase several years ago, because all my friends flip positive when I loan them one.
The Gatekeeper-X1 that I purchased is a very simple unit & a very well conceived piece of gear with 3 to 4 inch ferrite tubes covering the hot & return leads with capacitors & surge protectors going from hot & neutral to ground. Given the cost of the box & hospital grade connectors, it was clearly a great cost effective product, & I would buy four more in a heartbeat.
About the newer model with the slow turn on- in principle an excellent idea to prevent in-rush current in power supplies with large electrolytic capacitors, but I do not know it is implemented- whether it current limits when fully on: relays can be current limiters. So, about that product I know from nothing.
However, fuses were previously mentioned, and fuses have presented a sonic degradation in every piece of gear I have designed or owned over the past 40 years. I either jump them or use the largets that will protect critical circuits in case iI do something. I bypassed the fuse & power switch in the 2 WBL Gatekeepers for my amps: the units supplying power to my 600watt monoblock amps. 20Amp toridial balanced transformers are my second alternative. They are excellent filters when uses correctly & are very quite, but very heavy.
Cheers,