You have to ask yourself why you want a sub. The obvious answer is for LFE in movies. There's a less obvious answer though. Bass out of a sub may sound better depending on your room acoustics. The sub will give you more options in that regard provided you need them. Also consider the size of your room. What is the lowest frequency that can be heard in your space? Also keep in mind the 350 low frequency response is pretty much the same as the LFR. And I don't think the 350 has a phase control which is important for synchronizing at the crossover frequency.
