The "e" models are newer and have some additional features / improvements. The 402 had a standby power draw of 370 watts. The "e" models have a very small power draw in standby (2 watts). You can also re-configure them to have the standard high power draw in standby mode if you wanted (essentially keeps the power supply and amp boards running).
The newer "e" models have improved transformers and looks to have larger power supply capacitor bank.
