Quick Question On Powermacs???

Yep, you can add both at a later date – although you'll have to use an external dongle for Bluetooth (as far as I'm aware you can't add the internal module yourself). You can just pop the dongle in a spare USB port round the back of your display or something, it works just as well.

 

Airport Extreme - yes!
Bluetooth - yes, but not with the BTO (built-to-order) Bluetooth that Apple provides (that's not available separately). You would have to go for a USB Bluetooth adapter like the D-Link DBT120 and connect it to your USB port - it costs around US$30-40.

But if you're looking at bluetooth in the near future to use with a wireless keyboard/mouse, then the BTO wireless keyboard/mouse option from Apple seems to be a good deal for $99. Getting these separately (even non-Apple brands) could be expensive.