new volfenhaug 12's

If the manual tells you 2,4 or 8 ohms, they're DVC 4ohm subs.  With two of them, here are your wiring choices:

They SAY 2,4 or 8 ohms but the choices are really 2 or 8 per sub.  The 4 is thrown in there because TECHNICALLY if you use just one voice coil the sub will be 4 ohm.

(If the subs are NOT DVC 4 ohm, post a response and go no further.)

The second diagram above, with subs wired series/parallel, is the only way you can go.  This setup should work with any amp.  Whatever Rockwood is, they should provide you with a user's manual to show how to use the features.  But here is the basics - the gain is the input level control, probably a screw.  Turn it counterclockwise all the way to the stop.  With the system setup completely and subs wired as shown above, play a CD.  You will barely hear it, but turn the deck up until the sound gets like it sounds "forced".  That should be about 3/4 up on the volume control.  When you get to that point where you hear the sound start to sound strained, turn it back down a little.  That's the maximum clean output of the deck.

To set amplifier gain at this time, turn the screw clockwise slowly...the sound will come alive.  It may not take much of a turn to get to the point where the music starts to lose its clarity, sounding "strained".  Just like you did with the deck, turn the amp's gain back down a slight bit until you are satifsfied that the music sounds good, although it will be at maximum volume so be careful.  You have now successfully set the gain.

Bass boost is for idiots, so leave it off or at minimum.

An amplifier will have built-in active crossovers for high pass (to speakers or components) and low pass (to the subwoofer).  Take your time listening to a variety of your favored music sources and adjust those until you have a smooth transition of sound from the speakers to the subwoofer.  This part doesn't have to be scientific...it's all about how it sounds to you.

I happen to have two of the comp. Volfenhag 12's.... And they are set up on an Autotec Mean Machine. I ran them parallel on the two channel for a 2 ohm stereo load. In the box I built for them they sound pretty good. They are comp subs so I entered and hit almost 143.0 on a Term-lab at a Usaci Outlaw event. I havent had any loudness issues out of mine, and sometimes it gets to be over-powering to be honest... Hope this post is helpful and not too late.  B.W.