Audio Systems: Calculating impedance with a sub-woofer, internal amps, denon dra

Question
I'm trying to figure out if I'm over-doing things with multiple speakers on my Denon DRA-425R receiver.  The receiver says on the back 6~16 Ohms A or B and 12~16 ohms A + B.  Looking at "A" I have an Advent ASW1200 subwoofer which is rated at 8 ohms and a pair of Harman Kardon satellites, also rated at 8 ohms. Normally, two 8 ohm speakers would result in total 4 ohms of impedance--but does the fact that the satellites go through the powered subwoofer change things?  (That is, since the sub-woofer has its own amplifier, does it even "count"?)

"B" is even trickier.  I built the speakers with a separate woofer (6 ohm), midrange (8 ohm), and tweeter (8 ohm), and of course a crossover.  How do I determine the total impedance of that?

Answer
The subwoofer is self powered and does not connect to the internal amps so does not count.

The crossover system will be giving the system it's own imppedance. Probably around 7 ohms but you must measure it to be sure.

Be careful not to have a load too low in impedance or you can damage the. amplifier.

good luck.