I have stackables. But I don't know about buying more of them. The issue I have with them is that stacking them creates longer and longer levers inserted into your modules. It becomes easier and easier to accidentally bump those stacks with your hands. Depending on the module you could do some damage to the jack or circuit board below. I would use Y cables for anything that's directly inserted into a module or using an outboard passive splitter like those made by Intellijel.