You're going to use it's integrated graphics? You need the fastest RAM you can get and run it in dual channel. 1866mhz at least.
You can easily overclock the processor, but you would be better off overclocking the igpu part of the chip.
Overclocking depends on several variables like motherboard, cpu cooling, chip quality, etc...
Some A6s will overclock better than others. You may or may not get the same overclock out of yours that somebody else has.