maxed out Xbox 360 storage

I believe this is the most possible storage you can have on an Xbox 360 at the moment:

There is a 120GB hard drive, the 256MB of onboard flash memory, two 512MB memory units, and the 192MB that comes in the HD DVD player.
Of course you can't actually store anything in the HD DVD player memory, but it is listed.

to summarize:

120GB

256MB

512MB

512MB

192MB