I agree, unless space is just that much of an overriding concern you're just gonna have an easier time in general with an ATX case... Less sweating over fitting everything in and easier to score a better value. There's some pretty small mid towers out there, you don't have to get a 20lb monster.
I'm partial to the DT 880 myself obviously but you'll want a decent amp for it... Been reading good things about the Zx, tho I've no clue how it's virtual surround stacks up against older cards.
The Promedias are a waste of $100 unless you just want a rafter shaking one note sub tho, I'm usually not that blunt or crass but I just don't think they're worth $100. No sub at that price point's gonna be spectacular anyway, but much less a sub that's forced to make up for underpowered/undersized satellites.
I'd sooner recommend blowing the entire budget on source/amp/headphones than waste any money on the Promedias (or most PC speakers, and there's far worse sadly), but that's just me.
If you guys think the headset market in general is vastly undeserved and not generally a good value proposition, you should take that and multiply it by a thousand, that's what the PC speaker market represents (even compared to the lowest budget bookshelf speakers).
Edited by Impulse - 1/27/13 at 10:39pm