Conflicting impedance specs for Definitive Technology Demand D9 speakers

Looking at DefTech's website, they list nominal impedance at 4 ohms.  The included manual from DefTech states that they are "compatible with 8 ohm outputs."  All of the retailers that list specs for these speakers (Best Buy and Crutchfield) list nominal impedance at 8 ohms.

I have my pair running through my Marantz NR1200 and the default impedance on the amp is set at 8 ohms.  I'm admittedly a novice when it comes to some of these matters, but I'm just wondering what effect I'd see if I switched my receiver to 4 ohms impedance instead of the default 8.  Thanks for your help!
The best way to learn is to try and hear for yourself. Run it the way it sounds best. Sorry, but all the tech talk about impedance is.... tech talk about impedance. Its nice to know. Because who knows, some day you might hook up a bunch of speakers and the amp shuts down or overheats and its nice to understand why and know what to do to fix it. But that's about it for tech specs. They are useful only when you know what they are useful for, and don't try and as they say put legs on a snake.

As part of understanding, nominal in this case means average, or whatever the manufacturer wants you to think it is. Impedance in reality goes up and down all over the place depending on frequency. Some speakers can have some really nasty impedance dips. So when certain speakers sound like crap with certain amps sometimes guys who like tech talk claim its all about impedance and the amps ability to deliver current. See, I can do tech talk. Its not that hard. I just don't. Because its just not that useful.

Learning to listen, and select what sounds best, that is what's useful.
Sounds good to me!  I just wanted to make sure I wasn't going to burn my apartment complex down because I flipped a switch in my amp.  ;)
Funny you mention, according to some here I must have burned down my house, and probably the whole neighborhood, several times now based on the stuff I've done.

That one innocent looking picture of a simple resistor mod? Was told if I tried it would kill me. Blow the amp, kill me, burn the house down. Even if the amp was unplugged. I am NOT kidding! So be aware- not all interweb advice is created equal.