Yup, getting a properly matched left, right, and center speakers should make a big difference to your movie watching experience. Also make sure to use the supplied mic/YPAO system to properly calibrate it.
Due to limited space currently and an adventurous 2-year-old, I'm just using two small DefTech speakers up front and a cheap 10" Velodyne sub. No center, no rears. One of these days I'll do a proper HT setup again...