Ideally yes. Ideally the sub should match the speakers - not only should it be designed with same Q or damped response to preserve timbre but also to get better phase accuracy through the crossover between mains and sub. If it is mainly for movies then I would not worry about this though - just use the matching sub for music and both for HT.
2nd powered subwoofer
Is it absolutely mandatory to use the exact same brand and model subwoofer for use as a 2nd unit in the same room? I'm looking to just supplement my main sub (B&W ASW600) by adding some LFEs in another part of the room to balance and even out the bass. I don't have the budget for another B&W ASW600 series subwoofer. My AVR has two subwoofer outputs. If I do use a different size and brand, will this end up being out of phase and sound funny? What else should I be aware of in this move? I couldn't find any info on this in my Robert Harley reference book, "The Complete Guide to High End Audio". Thanks.