Even 50/60 is very difficult. I have an i7 920, 6 gigs if 1600mhz ddr3 ran with 7-7-7-20 timings (quality stuff), and 2 gts 250 sli'd. I am just now getting 60 fps. And it does dip down to 40's in the benchmark utility. However even with one gts 250, it was playable. Maybe 25/40?
This isn't maxed though. Things lie draw distance and shadow density were set lower.
I don't know as much about the last gen on cards othe than the 9800 and the 250 (basically a 9800 ++) but I'm guessing you might need to either sli, or sell that one to buy another.