Wrong. My first idea was to put the APEx on the other side of the house low and extend our existing hidden, mac filtered, WEP (I know, I know, our DS's need them, shush) network. Turns out Apple HATES WEP (as they should, seriously) - the only security I could use was WPA & WPA2. Knowing Apple, I held the Option key and clicked again - well lookie there, WEP (Transitional Network) appeared! Okay, I'll enter my 26 character WEP key... doesn't work, only wants a passphrase. Holding Option and clicking any and everywhere does not reveal an entry box to put the 128-bit key. Fine, I'll figure out the passphrase that produces my specific WEP based on this piece of knowledge of how using a 13 character phrase's ascii results in a key... except I need to enter special characters like ∫ & Œ which the AirPort Extreme does not like in it's little box. Terrific. I could change the WEP key by using a passphrase, but then I'd have to change all like 50 of my devices from one dump security model to the same... if I have to change them all, I'd rather go to something more secure that just making a lateral change. So, what if I make the APEx my new base and use the old Linksys WAP54 to extend? Screw WEP, I need WPA2 anyway - let's do it!
Wrong. So I set up the APEx with this whole new network using dual banded 5 GHz a-n/ 2.4 GHz b-g (looking forward to juicing up some blazing speed) using WPA2, and then go to the Linksys WAP54 and tell it to be a wireless repeater. I push site survey, point to my new network and push connect... Nothing happens. Switch browsers, try again - error. WTH. Switch browsers again (having multiple browsers is so wonderful...) to try again - it works by adding the mac address of my APEx but it's red indicating no connection. A bit of Googling turns up that YOU CAN'T USE WPA IN BRIDGED MODE. What. The Hell. Now what?
DD-WRT (robust open firmware for Linksys and other routers) to the rescue! After navigating to the hidden firmware page and flashing the latest beta build via the router database page, I was rocking... and had no idea what to do next. After intense fighting for hours, I found this simple walkthrough of setting up a wireless repeater bridge - and I was finished in 5 minutes, with WPA2 working perfectly. SWEET.
Lastly, I grabbed a 2TB green WD My Book, deleted the default FAT32 partition and created a HFS+ with Journaling partition using GUID (by default most large hard drives are using MBR partition schemes which Time Machine can't use) and plugged in - *poof* a giant, gigabit & USB 2.0 speed data drive is out there for general and Time Machine use! DOUBLE SWEET.
So that is that - we've finally updated to real network security and have a backup plan regularly running (daily not hourly) and it only took two days to get it all working (if we had these links it would have taken 30 minutes, heh). Now let's hope I don't have to redo entering 50 mac addresses if a new APEx comes out tomorrow... ^_^