I think the board defaults to 1333 MHz anyways, you need to "OC" the timing to meet the stated timing of the RAM. If I'm not mistaken, MSI considers 1600 MHz an OC setting, so it'll be 1333 MHz default.
I own this exact board and I noticed that if I tweak my BIOS settings, (As in I overclocked my CPU only) then it will change the timing on it's own (the BIOS changed the MHz of the RAM automatically).
I'm not saying OC your CPU to make the RAM meet the advertized specs. But you should be able to OC the RAM and make it work.
For all the rest who own this board... CHECK the timings of your RAM and your BIOS. I had to RMA my board because the board set the RAM to 1600 MHz when I had 1333 MHz RAM. It caused the board to freeze on boot, it won't even post. However, it's not a bricked board, you can just swap the BIOS for another or reflash it, but I happen to have just bought this board within 3 days. So RMAed it
EDIT: I didn't answer the rest of your question... to boost it up you need to go into BIOS and go to CELL MENU and then the RAM setting should be below the CPU Clock. I believe you need to enable something to tweak the RAM but that option is on that page. From there I can't say exactly what to do, because my board is on it's way back I can't boot up and guide you through it step by step, but it shouldn't bee too hard.
As for how much of a difference it makes... I don't think you'll see a difference if you tweak the timing from 1333 to 1600 unless you run an intensive game or program. However, I do think that if you install more RAM you'll see a much more noticeable speed difference especially if you run Vista or Windows 7 because those OSes were made to use the ram you have available and not to waste any. If you can export more programs into ram then you will have faster response times from more things rather than just the high end software. That's what I know and that's why I figured having 16 gigs of ram versus 4 should make more difference than going from 1333 Mhz RAM to 1600 Mhz.
Another side note... I think most DDR2 RAM runs at or near 800 MHz, and DDR3 goes to 1600 MHz. So just having DDR3 RAM should make *that* much more difference, but I don't know for sure. CAS timings on DDR2 RAM are way lower than DDR3. DDR3 RAM I believe was designed to handle more memory at once than DDR2.Edited by DarkRagnarok - 1/26/11 at 2:10pm