So I've been reading around on these forums trying to answer my questions. I've mainly been successful. I'll be using these cans for mix downs at my own home (quite, and away from people), so I've concluded open cans will work best for a truthful, neutral sound that will ultimately translate well to virtually any system that isn't eq'd weird.
I'm still kind of between the 880s and the 990s, leaning a little toward the 990s because, best I can tell, they are a little flatter which is better for the original mixing. My question is, plugged into an E-Mu 1616m ( http://www.emu.com/products/product.asp?category=505&subcategory=491&product=15189 ), will the 600 Ohm versions be adequately powered, or should I just stick to the 250s?