Speaker upgrade
Since you mentioned EMP, check out their on-wall speakers for the front 3 channels, for $100 each. Add 1 or 2 pairs of the satelites for the surrounds. The freqency response and SPL capabilities of satelite speakers tend to be limited by their small drivers, but the EMPs include 4" woofers.
The sub does not have to "match" the other speakers and ID companies like SVS, HSU, and AV123 are good options for the sub.