What counts as a custom configuration?

I hear that Apple Stores don't have custom configurations available. My question is what counts as a custom configuration?

I'm planning on buying a iMac 24" 3.06GHZ 512MBGeforce 8800GS. I don't want to modify anything but I do want the following:

-- Wireless Apple Mighty Mouse
-- Wireless Apple Keyboard
-- Applecare

I know Applecare comes in a separate small box, but the other two would normally be packed in the box as wired devices. On Apple's online store you can upgrade to these devices for $30 or so each instead of paying full retail for them separately. Does this count as a custom configuration? Will the Apple store slice open the box and drop in a wireless keyboard/mouse and charge me the applicable upgrade rate? If I want these at the extra cost, would I have to buy from the online store? I might as well ask here and save a trip to their store if possible.