Hey - similar RAM in consideration, but different situation. I have a Gateway FX4710 with a stock G33-chipset motherboard, and I recently bought 2x2 GB RAM of two types: Patriot Viper DDR2-800 and OCZ HPC Reaper DDR2-800, both of which are rated at 4 CL at 2.1V. However, I wasn't aware that the motherboard's voltage is only set at 1.8v, and since it's a OEM, there's no way to change the voltage in BIOS. I've been having problems with crashes if I use the OCZ and Viper in all 4 slots, but not if I only use the OCZ in two slots OR if I use the OCZ with 2 sticks of my original 667 RAM (in which case all the RAM is running at 667 instead of 800).
I'm wondering if OCZ HPC Reaper (http://www.ocztechnology.com/products/memory/ocz_ddr2_pc2_6400_reaper_hpc_edition) can actually sustain running at 1.8V if I put in 2 more sticks of them. So far they seem to be doing OK, but only with two sticks of them and two sticks of 1.8V RAM. I'm definitely returning the Patriot Viper sticks since they do not run, even by themselves, on 1.8V.
The other choice is to return everything and buy 8 GB of 1.8V 800mhz RAM at 5-5-5 timings, although I would prefer using the OCZ Reapers if they work. This is because I do plan on replacing my PC's motherboard in the future, and I suppose they are more versatile if I do decide to OC then.
Posted this elsewhere, but I hope I can get some more responses since I need to decide soon to return or not. Thanks - Tilted.