Its the Gigabyte 965P S3 that's an overclocking motherboard, not the 945PL. Those are the names of the chipsets, and they're what determine most of the motherboard's overclocking capabilities.
The $115 Gigabyte that I linked up there is better than any other motherboard talked about in this thread. The Biostar 965P and that Foxconn 965P are in the same league, just take your pick. Don't pick that Gigabyte 945P that you linked up there.
As for the memory; All DDR2 is not the same. DDR2-533 is the base memory that you need to run your system without anything overclocked at all. DDR2-667 allows for a little bit more overclocking, but nowhere near enough to get you to any noticeable performance increases. DDR2-800 is where the real performance is. DDR2-800 lets you take your E6300 to 2.8Ghz guaranteed (assuming the processor can handle it). So stick with the G.Skill that I linked up there. The E6300 is a low-multiplier processor (7x) so it's already hard for it to overclock. Higher-multiplier processors (9x, 10x, 11x) can overclock a lot farther with the same speed memory. For example, a E6600 has a 9x multiplier. DDR2-800 gives the E6600 the ability to overclock up to 4.0Ghz guaranteed, if the processor can handle that.
Don't skimp on the parts in favor of saving money, you're only going to regret it later. Speaking from personal experience here.