Should I call and change my order to a 1.8 V memory with the right timings or will I be able to make adjustments in the BIOS?
No! and Yes!
Your mobo will probably default to 5-5-5-15 and 1.8 volts.
Pop in your memory, enter BIOS and change from Automatic to Manual and then enter your timings 4-4-4-12 and don't forget to also change the voltage to 2.2V.
You just might need to turn up the voltage to 2 Volts. I have heard of a few pep's that have trouble because the mother board defaults to 1.8 V and the DIMMS won't run at low latencys and low Voltage. The fix is to put one cheap 667 Mhz Dimm in and Boot to BIOS then make the adjusatmant then install your DIMMS. It's a pain unless you have DDR2 DIMM Laying around. I purchaced a 512 G.skill DIMM and keep it in a drawer for this purpose.
The previous poster is almost right, to access the memory timings in the F11 DS3 BIOS (like the F10 bios) you need to press CNTRL F1, not CNTRL F11. This must be done on the 'welcome' screen of the BIOS set-up.
Good Luck. I have the same set-up and i am running 900+ at 4-4-4-12 but just recently i have started using memtest and I am getting some errors.