You may not need another RAID controller, but you most likely won't achieve that level of write performance using 4 of those hard disks. You may be able to exceed the results achived at http://www.extremetech.com/article2/0,2845,2334985,00.asp,
but it would still be way below your requirements.
might help you decide on the optimal solution (they used SSD drives). As you can see, the ICH10R performs quite well. Even a RAID 5 configuration using 3 SSDs would be fine. You should be mainly interested in the minimum write performance.
Four 15K SAS drives on a caching RAID controller with BBS might meet your requirements, but it still would be significantly slower than SSDs.