They have some Corsair xms2 2x1gb ddr2-800 cas5 for about 208 after rebate on Newegg at the time I checked. Zipzoomfly has some 2x1gb OCZ platinum revision 2 ddr2-800 for about 190 after rebates I believe. Check out other online stores yourself and do some comparisons on prices etc. as anything not of the higher rated d9s are getting cheaper again it seems. This should prep you if ever decide to go Vista next year or later this year. More importantly, you won't have 512 modules taking up precious space if you ever decide on 4gb total for Vista. You can get the good micron d9s for around 300 USD but honestly, it's not something I'd consider too closely at the moment on your budget or any budget for that matter unless you are going top of the line. DDR2-800 should allow for a bit of OC room without taxing the memory much and keeping to 1:1 (also depends on your processor and mobo though.) EDIT: Just keep in mind not to spend too much money on RAM as ddr3 is coming. Of course, that doesn't really apply to you unless you upgrade as soon as they switch but prices for ddr2 may grow cheaper with demand lower.
I'm not sure you should grab anything more than that for your video card till you find a DX10 only must have game. Games with DX10 code paths should come out around next year I believe so you might want to adjust your budget accordingly. You might even want something slightly cheaper to just tide you over until dx10 games go big.
I don't think Coolmax is a recommended PSU brand unfortunately but the Fortron mentioned is considered entry level these days on enthusiast boards and a lot of people link to it. You might consider getting a bit more expensive PSU than the Fortron if you plan on updating this system later on for more juice. I'm sure someone has the recommended PSU link somewhere.
For the motherboard, you can step all the way down to a Gigabyte S3 depending how strapped you are. People don't like it because of it's lack of solid state capacitors and a few other issues but I feel it's one of the better entry (enthusiast) level boards for the c2d platform. There was also a Biostar mentioned but honestly, I've never encountered it and none of my friends have that board so you'd have to read the reviews. If you stick with the p5n-e (which isn't a bad choice), you have to realize that it does have it's fair share of issues in terms of memory etc. Bios revisions for this board are somewhat sparse and it's not nearly as stable as p965 chipset (on average, intel chipsets are much more stable compared to the nvidia ones at the moment for the c2d but that will hopefully change over time.) On the flipside, the p5n-e is still rather cheap for the performance and offers SLI and a hd IDE for those older hard drives in case you have any lying around. Perhaps even more importantly in your case, it also offers some async memory overclocking if you decide on cheaper memory that can't cut it. Every board does have it's quirks though and the p5n-e has more than it's fair share in my opinion. The 401 bios is supposed to be great but I've yet to try it out. Other things of note: You should probably buy a chipset cooler of some sort or attach a fan to the north bridge if you are going to do any serious overclocking. Any dinky heatsink will work on the southbridge but make sure the heatsink isn't too large/tall or you can't do SLI in the future. Very good airflow might be enough but not recommended - at the very least, it'll cost you 5-7 dollars without shipping for additional cooling. You could go all out and change the northbridge entirely but it doesn't seem necessary to me.
You would benefit from an e6600 since it's clocked higher and more importantly, has 4mb of l2 cache instead of 2 so an e6400 might be harder to justify the cost with the impending price decrease. You could go for an e4400 or an e6300 at the moment and overclock that. Both are at similar prices right now so it's up to you what you want to get there (people would probably say the e4400) but you could skimp right now and simply wait for a better processor to get cheaper and buy something better later when it's also cheaper (like quadcore... right.) By the way, you can get a decent overclock with the stock intel heatsink. Otherwise, you should probably go with the arctic freezer pro 7 since it's cheap but I'm going to write this off as an unnecessary expense for your build at this time. You can always go back and purchase this later.
Hard drive is up to you but seagate 7200.10s sport perpendicular recording to my knowledge so you might want to consider a .10 release of similar size.
Uh, possibly you might want an floppy drive. Maybe not as you can flash from the USB for the p5n-e but it's something to consider especially since some recovery programs and the like still use floppies.
Disclaimer: The above is my complete opinion and I could be and more likely am 100% wrong.