Hi, you can try the (cheap, red colour) LED bias - schematic and wiring details are here. Center of your loctal socket can be a "local" (driver) grounding point, you can solder the minus pole of your last filter cap (from the driver supply) here, too. From that point, one wire to the one and only star (chasis) ground point. R1 and R9 are "stopper" resistors and must be non inductive, HQ (say CC or tantalum), and soldered close to the pins. Two red LEDs are connected in series, their leads must be short, too. Of course, CCS version is showed, for interstage version you must make some minor corrections.
Interestingly, with my speakers I have almost too much those low mids, ha. Deep bass - yesss!
Try this, and please report back...good luck!

• http://www.audioroundtable.com/GroupBuild/Projects/SE300B_C3g_driver.jpg