Extending AppleTV Hard Drive

I have a 400GB AppleTV (hacked) and a 1TB external WD USB drive … can I use the WD as an extension of the 400GB on the AppleTV or must I use one or the other but not both?

thanks in advance

The 1TB can be used for secondary storage while iTunes syncs to the internal, or you can set iTunes to sync only to the external drive.

How do you play things from the external drive if you are syncing iTunes to the internal?

When connected the external drive will be visible through the nitoTV --> Files menu.