|If you use frequencies rather than the bogus FSB & DDR ratings, it should make more sense. For most Intel based systems (other than P4 & the Core i-series), there are two CPU:RAM frequency ratios that are considered optimal...1:1 or 1:2. Here's what you currently have:|
1333MHz FSB = 333MHz frequency
1066MHz DDR = 533MHz frequency
Your ratio is 333:533 which is 5:8. To get to 1:1, you'd have to reduce the RAM frequency to 333MHz (667MHz DDR). To get to 1:2 ratio, you'd have to increase the RAM frequency to 667MHz (1333MHz DDR).
Personally, I wouldn't waste any money on RAM. If anything, invest in a graphics card & tweak the OS for best performance.