It is just a tweak, i had one of those Musical fidelity ones. It was attempting to be a bandaid fix for shit SS. I sold it but i kept the musical fidelity watch that came with it.
It sat in the face of my system build philosophy. It didn't offer anything i liked about tubes. Just added more distortion with a bloated texture to it.
There is a technique in rpg gaming that fits and can be applied to building stereo. In on line gaming there is technique for building online characters. Its called min-maxing. Basically you take a particular attribute offered and you maximize that attribute. If you build a character around strenght. You take all strenght gear and strength talents and maximize. You rid all the gear with stuff making you faster or protective. This makes that character perform the best under strength performing activities. You basically maximise that attribute. If you don't know how to do this it basically illuminates you from raiding or participating with any serious goal minded guilds.
It's the same for stereo building imo. If you going to build a system around tubes the idea is you maximize the tube placement in gear. Basically all tubes then you can ease back on with cabling or tube changing.
So to me it does not make sense to put together an SS system then apply tubes. Its losing the initial musical intent of the system build.
There are always exceptions but i really do not believe building gear around (the possibility of) exceptions is a good method.