You can find the EBTech Hum Eliminator at many online sites including audiomidi.com

Yes it is very simple to use, just put it inline between your pre-pro and the subs. The two-channel one would likely be ideal for your two-sub situation (assuming that your subs are not simply defective). If you use the usual RCA connections to the subs then you would want to get four 1/4"-to-RCA adapters from RadioShack as well.

EBTech also has the new Hum-X product which would also likely fix for your problem.

Here is a link: http://www.audiomidi.com/HE-2-Hum-Eliminator---2-Channel-P314.aspx?CPID=392&AFID=3