Well, I dont like making suggestions without being sure..
Even if the math and enginnering I post is correct that does not mean the application, in your case that BIOS, was using that math or formula.
I have seen Asus and other MB manufactures do some really off the wall things over the years so better safe than sorry
But you got it now so I would not upgrade that BIOS again and keep what you have which is stable unless later you move to DDR3 2000+ and need another BIOS upgrade for it.
but I would wait to see if they further improve the timing and lower the price before making that move