Just get the slower RAM, if the price difference is that big. DDR2-1066 will not give a slightest bit of real-life performance gains over DDR2-800 (again, I'm assuming that the latencies are fairly good, 5-5-5-15 for PC6400 at max.), unless you have the memory in single-channel and are running some really memory-intensive applications (I don't think even Crysis would see significant performance gains).