Sub Positioning

The sound of bass will be the same pretty much anywhere in the car, it isn't the same as the higher frequency sounds from your mids and highs. If you were to have somebody moving the sub around while you listen to it, you wouldn't be able to locate its position. As for the angle of the subs, the way I have mine makes it extremely loud in the cabin of the car, but my trunk rattles a bit (but not as bad as one would think). Check out my setup in my sig.Jon

Don't like rockford subs? Then don't look at my car =)

IMO, the angles of each enclosure should be the same....straight to the rear or straight to the front, and experimentation will give best results.  If the enclosures are designed so that they will fit only one way, I would choose straight to the rear.  As far as which you should do first:  usually, there is a difference in impedance and thus amplifier power output when you hook up one first of a 2-sub setup.  Of course, you need to verify that you can actually run one without the other and not damage the amp.  As long as you can do it, which side first should make no difference.