Gurren Lagann DVD Part 1 (Hyb) (vol 1-2) Limited Edition (is the artbox supposed to house the complete series?)
As I understand it, yes. You can take some comfort in the fact that the term "artbox" is used almost exclusively for boxes used to house full anime collections. If you look at the picture really closely (CTRL + mousewheel in Firefox or IE to zoom if it helps) and you can likely make out that it appears to have room for at least 4 volumes. I'm just hoping the second LE set has the OST since the first doesn't.
Eureka Seven DVD 1-12 (anyone got any clue on an artbox, or is it never gonna get one)
Actually it got two artboxes. LE volumes 1 & 7 are what you're looking for I believe.
Silent Mobius DVD Complete Collection (Hyb) (Anime Legends)
or ------whats the difference between these
Silent Mobius Movie 1 DVD (Hyb) Limited Edition + CD
Silent Mobius Movie 2 DVD (Hyb) Limited Edition + CD
If I'm understanding your question correctly the complete collection is of the series itself whereas the movies are just that. The LE editions come in a steel case like you may have seen with the Hellsing
and Black Lagoon
LEs. And of course who can forget those sweet, sweet OSTs... Nice wishlist BTW. I'm also looking forward to seeing .Hack//Roots
make its way to "complete collection" status.