Don't give up just yet. Are you sure something isn't running in the background? Probably the detail and AA I suppose....
I wish I understood all about graphic cards and RAM and Giga this and Tera that, because it always seems that something doesn't jive when your drive shows like a tenth used and renders go so slow. Someone could explain it to me for a week and I would still not get it, so I go with what I got too.