I have a Coolermaster 830 currently.
Despite the primarily aluminium construction it's pretty heavy.
I tote the thing back to my workbench quite a bit to work on the case or the watercooling.
It has handles built in and is still bulky and heavy.
I have an old Chieftec Dragon full tower, all steel, that would be about the size of this Obsidian case..........and it is way heavy, almost immobile.
Weight aside, try a dremmel on steel..........might as well go home and cry.
Aluminium is much, much easier to drill and cut, making a modification an hour instead of a day long chore.
Just 2 cents, that's all.
I've had the Stacker 830. It is heavy, no doubt about that.. I wouldn't call the Chieftec Dragon immobile even when loaded. I've had the Antec counterparts to those. I've had 3 of them in fact. Try and Antec P190 with water cooling, 3 video cards, and 8 hard drives. That's a heavy bitch. Still I can manage it just fine. I never did move it often. As for drilling or using a dremel on steel, well all I can say is that I've never had a problem with it. My 18v DeWalt XRP goes through that case like butter. Get the right drill and the right bits and it shouldn't be an issue.