LateX in all honesty if you are planning on overclocking it, get the Noctua cooler, and some corsair XMS3 memory, so there is not problems fitting the cooler.
If u get the mega, it costs the same as u have to add 2 fans to the cost. With the mega you are looking closer to 80'c temps for 4ghz, the noctua your more likely to be looking at 70/75c, and it will be quieter.
And yup the noctua comes with 2 fans ready, so no extra cost.
There really is'nt much difference with the memory, maybe cas ratings, but u will never notice that day to day, only in benchmarks.
Also you asked about the Psu, its more then fine, so don't worry about it.