Typically the only circuits in our North American houses that have/need dedicated 240v. are Stoves and Dryers or Large shop tools. The 240v. is for users in other Continents.
If you were to put a dedicated 240 outlet for just your sub/subs is total overkill. Staying all 120V. is sufficient. The EP500 has it's own Toroidal power supply as well.
Sole dedicated line Much better use with for your AVR/Amps/ C.D. Blueray etc. Aficionado's with BIG Amps. recommend a 120V. 20A line Maximum for high power demands 30A Will potentially fry your equipment
As a total anti Ground loop scheme each Outlet should be direct to breaker for ultimate trouble prevention.
