An Asus WL500g with a USB hard disk attached, and it worked very well. Some of the WL700 series have a hard disk built in as well.

They're considerably cheaper than Apple's offering, and are also very capeable wireless routers with plenty of good custom (they're GPL) firmware.

I have the 500GB version at it is ok, the router is basic, and dose not have some of the functionality that most modern routers now have, for that reason i have stuck with my old Netgear for the internet routing, but as network storage its great, you can plug an extra drive it to it, and if you have powered USB hub you can plug more than 1, I have three external drives running through it and a printer and they work fine. It is easy to set up through a Mac, unless you are complete idiot, you can have it up and running in minutes, I have it joined to my current wireless network and performance wise its ok. I have lot of media files stored on it and they stream well over the wireless, even with time machine backing up in the background. All though I find the router side a bit disappointing, overall its a good product and the fact you can add extra USB drives and printers to it is a bonus. I am very pleased with mine. The only thing I cautions on is it dose get hot, I mean really hot, you can cook your breakfast on it. So make sure you give it some breathing room.

I'm unsure what functionality a Netgear offers that the TC doesn't? The Wireless is speedy, the fixed line is a little slow for a true Gigabit but still much faster than Wireless.

You have top notch security - even USB added HDD's can be password protected..... iCgat, Back to my Mac etc all work seamlessly if required.

I personally prefer it in its simplicity to any other home router i've used, it's never crashed, is silent, the hard disc read and write speeds are excellent and Time Machine backups for the Macs will be useful for you.

For what you're after there may well be cheaper options but i doubt they'll do it all so straightforwardly and easily... i say buy one.