Always focus on getting the best you can afford for all 5/7 speakers. Don't cheap out on the center or surrounds either, especially the center, since >60% of the soundtrack is anchored to it, many people will pair their fronts with lousy surrounds, claiming they're "barely used". I think this conclusion is reached BECAUSE people use lousy surrounds that can't keep up with the LCR, not because there's actually not much content in them. Even many TV shows I've watched have fairly active surround content.
Don't make the mistake of purchasing big towers for the L/R and puny satellites for the center and surrounds.
In addition, it's always best to timbre match all speakers as closely as possible. Using different lines, or worse, different brands of speakers for the surrounds or heights is distracting, and ruins the seamlessness of the sound stage IME.
What is your budget, room size/distance from the TV, and goals for the system? Luckily, in 2018, an excellent, high performance system can be designed on any budget.
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