I believe the cosmos case is steel and the stacker is aluminum although on hexus.tv hey said the cosmos will be out in about 3 months in an aluminum version. (still havent figured out why some people dont like steel)
Both of these cases were on sale at NewEgg several weeks ago at incredible prices. I came very close to buying the 832 but backed away when I heard of Antec's new 1200 case that is coming out.
The Cosmos does not appeal to me. The case is absolutely gigantic in all dimensions. At a local store I lined it up next to a 832 and my current case, an Antec 180B. The 180B, which is not exactly a small case, looked like a minibox. The 832 black, which is what I was comparing, is larger but has enough details on it to give the impression of being large but still within reason. The silver Cosmos is simply in your face in every manner. There is no way it could sit on a desk.
Visual effects aside, the Cosmos also suffers from a problem that is clear the instant you take the side covers off. The hard drive chambers look like a vault. Yes, they are securely installed but there is no airflow at all. At least I couldn't see any. From every angle the drives are locked inside of a closed box.
The 832 is also a hassle with the hard drives but not in the area of cooling. Their problem is that you need to remove the entire cage (screws on BOTH sides just like the Antec 900) to work with individual drives. Forget that. From pictures I have seen of the new Antec 1200 it looks like they may have changed their build to deal with this stupid time consuming problem. It is certainly a big advantage to the 180/190.
One last point. I spent a lot of time removing and then replacing the side covers on both the 832 and the Cosmos as nearly every review on NewEgg complains about them. The 832 is doable once you get the knack. After 30 minutes of so I still couldn't get the Cosmos covers back on without a major hassle. And for a case that will probably rest on the floor that makes this even a greater issue. It is not a case that you pick up and easily move around even with the massive handles on the top.
If you find somewhere locally with both the two cases (Frys has them) definitely check them out. These are cases that need to be seen as pictures do not give the full impact. If that's not possible then take the measurements and apply them to your current case. Better yet, build yourself a cardbox box. You can always use it as a spare bedroom afterwards. The Cosmos is that large.