I use the Gold xTreme. In my system, I can tell a difference from the silver. I think they just started selling a smaller kit, so you can save some money.
I used to think it was "nuts" to clean my ac contacts, but then I tried it and heard a difference. Just say I'm way less cynical about tweaks than I used to be. Some of what I thought were tweaks 10 years ago are now things I wouldn't even consider doing without, now.
Certainly nothing personal: you've raised a good question, but some people say, about any subject: if you haven't heard it, (ridden it, drove it, tried it on, shot it: from motorcycles, cars, clothes to shotguns) them you don't have an opinion, just a conclusion lacking support: I'll just go so far as to say that any audible improvement for less than $100 is a steal in this hobby.
Just keep an open mind. Sometimes a tweak is a difference, but not an improvement. Some of the reviewers were sceptical at first, and some people have thought that the metal content of eTreme and Walker made a change that they could hear, but didn't like, and went back to naked, but clean, contacts.
I couldn't hear a difference in Walker and Extreme, and the pro Gold is a good cleaner. I've never heard the Siltech.