I also hadn't heard of VCAs. (DCAs apparently are almost the same thing.)
VCA's (Voltage control amplifiers) and DCA's (digital controlled amplifiers) perform identical functions. They are analog and digital equivalents to each other. I have a feeling that Mackie just calls them VCA's because that is the traditional name. Digital mixers will most likely use DCA's. Subs are different in that they are a bus, much the same as the L/R mains bus. The VCA/DCA on the other hand, is not a mix bus. Rather, it controls the channels directly. Turning up a DCA is effectively the same as turning up all the faders assigned to it. So if there happens to be post fader auxilaries, they will be effected too. This is benificial because effects sends are usually post fader. Traditional VCA's were usually reserved for the high end analog consoles because of the costs involved in adding the functionality to them. The last VCA mixer I used was a Soundcraft MH3 but since then everything has gone digital.
Okay I'll acknowledge my limited understanding of WiFi RR. So, what is the cheapest way to get a wifi access point with a built in DHCP server? Is it to buy a standard router/switch/DHCP server/wifi access point such as an Apple Airport of some flavour or similar? 
Yup, that's what I said. Folks get all confused when they think of the DL as being "wireless" when it's not, and thinking that a network involves the internet, and etc...
Sure would be a lot more robust to have the DL have a static IP so it doesn't "miss" getting an IP if it is powered up at the same time as your DHCP server 
. I often have to change the power around after I'm first set up or the power gets otherwise interrupted and then you have to reboot the mixer after the router finishes booting. A mere split second power glitch often results in losing wireless connectivity and you don't really want to stop the show to reboot the mixer...
RR before you dig a deeper hole that your already in RTFM pgs. 147-154. You will find that the MF 3.x claims to have the ability to assign static IP addresses. Haven't tried it myself, too busy with other things. Probably want to do that docked and then set up the iPad if the address has changed. So you don't need a DHCP server since the iPad also allows static address assignments. Multihomed iPads are the WiFi and cellular connection versions. They can handle two separate networks. DL's of course are not included.
P.S. Behringer isn't the only one hiding features under edit 
.
I've changed my DL32R to a static IP. It works great and connectivity is rock solid. You'll find the IP controls in the device list. Look for the "i" inside the circle on the right hand side of the device list. Shouldn't be a problem running 2 mixers on the same network. However, you'll need to switch back and forth between them if you only have one iPad. Also, if you simply unplug the Ethernet cable from your mixer for a second instead of turning the mixer off, you can reestablish a connection without interrupting your show.
