Virj, if you're referring the "crossover" control on the back of the EP350(actually just a low-pass filter on the sub alone, rather than a full crossover), as Randy said, turn it up to the highest setting to get it out of the way of the crossover that your 2700 will be doing.
If you're using YPAO on the 2700 to set up, you might set it to skip setting the speaker crossovers and manually set all speakers "small" with an 80Hz crossover, which is a good compromise frequency, being high enough to relieve the speakers of a significant part of the lowest bass burden while not being so high as to make the sub easily localizable.
