Unsound, Herman and I agree on something :)
Herman, The reason the Trios and probably Duos have such an impedance curve has to do with the way the crossover works. Let's use the Duo as an example, but this is only an example, my experience with the Duo (even though a lot more of our customers use them than Trios) is limited.
So we have the main horn and let's assume that it is 8 ohms. Then there is the tweeter horn and it is 8 ohms too. Now if there is a cap to keep lows out of the tweeter, what happens is that at low frequencies the amp sees the 8 ohms of the main horn. Since there is no choke to keep highs out of the horn, the main horn will be in parallel with the tweeter at tweeter frequencies. So the impedance drops to four ohms because the amp has to drive the main horn and the tweeter too. The Trio uses an expanded 3-way version of this scenario.
If there is a crossover offered that has more than caps in it I think it will be a big step forward for that speaker!