Speaker & Wiring Impedance
Speaker impedance often is and should be straightforward. Speakers, like other resistors, wired in parallel "show" lower values than the individual components. In case you have forgotten, there is an example below for calculating speakers wired in parallel.
Often the real world is more complicated than the theory and for speakers this is the case. An eight ohm speaker is not eight ohms at all frequencies. Plus passive crossover networks add their own changing conditions. What you should be aware of and sensitive to are speakers that have significant dips from "nominal" values in portions of their frequency range and speakers that are rated at unusual impedances, for example 3.5 ohms. The Director is tolerant of lower impedance loads, however, all good designs use some margin of error.
Your choice of speaker wire gauge and the length of the runs also affects the speaker impedance load presented to the amplifiers. As you can see in this table below, even fairly short speaker runs can have significant resistance if you use a smaller wire gauge. This can be a benefit if you are paralleling lots of speakers. The wire itself acts as an impedance limiter, since the amplifier cannot see a speaker load lower than the resistance of the wire. The downside of this resistance in the wire is that you waste some part of the total power available to the speakers.