You don't need to match impedance and sensitivity of your different speakers, but you probably do want them to have the same tonal quality. If you like the Gallo A'Diva SE enough to use them as your main front left and right speakers, why don't you just use another Gallo A'Diva SE for the center channel? You then will have perfect voice matching with your other speakers.
As for the subwoofer, it does not have to match at all. It can be any brand you want. There are several good brands. SVS is one that is highly respected, and the brand of subwoofer I own. But there are other fine choices, and what you should buy depends on your budget, room requirements, listening tastes (i.e., loudness versus depth of bass required), etc.