I've owned the orginial 350, ep500v2, ep600v2, and 2 350v3's.
The ep500 was a huge upgrade from the original 350 obviously. The difference between the new 350's is much closer to the 500 and 600, but I would not call them equal.
The 500 and 600 go lower and play louder with no chance of distortion because of the DSP design. This is not to say that the new 350's distort, they don't because of the dynamic design. The 500 has a bigger amp and rolls off much lower.
The 350v3's are an amazing sub for the money, and I am continually impressed by the gut wrenching lows they pump out. Sometimes it is hard to tell that my 600 is in the mix.
