Increasing the RAM transfer rate from 800MHz. to 1066MHz. with an e6300 will not do much for performance. Leave the RAM speed at 800MHz. and increase the FSB. Both the CPU and RAM will clock higher that way. With that system the CPU overclock will make a difference, not the RAM so much. List the system specs including MB, RAM PSU, etc. if you expect help.
The true FSB of your E6300 is 266mhz, "quad pumped" for an effective rate of 1066.....to the processor. Everything else on the bus still runs at 266mhz.
That is why increasing the memory speed on pre i7 builds is kind of pointless. With the i7, they took the memory off the FSB, put the memory controller on the processor and implemented a type of hypertransport bus like AMD has. So if you bump up memory speed on these systems, you do get a little better results, as the memory is not bound by the FSB speed. However, having said all that, raising the bus speed of memory alone on a system, any system, nets you very little real world performance. Only small gains in memory read/write speeds that can only be seen in benchmarks.
In other words, if you are building a system, (not i7 or i5, these are different as I said) and you do not intend to overclock, do not look for the fastest memory by mhz, look for good 800mhz with tight or fast timings. This will get you better results. If you plan on overclocking your processor via the FSB, then memory with a higher FSB rating is desirable, so you will not clock it past it's rated stability.
As badge pointed out, if you really want to increase your systems speed, on your particular system, the way to do that is to increase the FSB speed.