the fc2 gains is a ripoff. they took some performance out of 9.3 to 9.4 and then decided to bring them back to make it look like theres a "real" performance improvement even when there's not.
the 4850s/4870s are well capable of those numbers before cat9.4. note: try to use cat 9.3. the only thing wherein i cant pitch my belief in is with the 4890. my theory is that cat 9.4 was a segmenting driver that was designed to properly segment the 4890 to a 4870, at least on farcry2.
i documented it right here:
http://www.tomshardware.com/forum/page-265155_28_50.html
you're not getting new performance, they just did what is due 3 releases ago.