The EP500 goes quite a bit deeper in the bass than the EP350. It has a different driver, DSP-based EQ and driver control to keep the frequency response flat, and enough power to handle playing both loud *and* flat.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8