I'd spend less on video cards and PSU and more on the CPU.
If you only want two video cards, no Triple-SLI, then 8800GTS G92 512MB cards are a better choice than 9800GTX. Almost the same speed, much less cash. The P5N-D is a 750i mobo and only allows two video cards anyway. You need a 780i mobo if you want the option to add a third later.
The PSU doesn't have to be 1000W. The 850W Toughpower would be plenty. The Silencer 750W would also be fine (with only two hard disks) and it has the added advantage that it blows the air out of the back of the case rather than to the bottom of the case where the airflow is blocked by the floor. Plus it's $100 less.
The Q9300 has a lousy multiplier which complicates overclocking. You can do better with a Q6700 or Q9450.
Add a Xigmatek HDT-S1283 cooler.
Do you really need a sound card? Are you sure you will still have a non-blocked PCI slot for it after you add two thick graphics cards? I suggest you don't buy any sound card yet and research that later. Try onboard audio first, it's pretty good these days.
I am not sure you know what you are doing?
What OS are you going to installed? XP or Vista? 32 bit or 64 bit? 32 bit OS only suppot up to 4 GB of ram, but only about 3.2 - 3.4 gig will be used due to address memory limits on 32 bit OS.
1000W PSU? Why? Are you overclocking? If so, are you over clocking to 20 Ghz? WTF Try using a PSU calculator. Antec has one on their website and it is pretty good. I would be surprised if you need this much power, unless you are planing for SLI and overclocking. If so, config the calculator with both configurations and see what it says.
I personally don't care for Corsair, Asus, or Evga. I believe there are better quality parts out there. Like BFG for the Video card, get a "8800 GT OC2" the 9800 GT isn't worth the extra money and both cards will be obsolete in 6 months anyways.
I like Kingston for Ram, HyperX is great if you can run 2.0 or 2.3 volts on your MB.
Sound Cards, I am a Big Sound Blaster Fan, I have been using them since forever. If you are gaming get the gaming card, if you want to save a few bucks get the Audigy 4, which is a great card for the money.
Personally I think you should wait on the video card just a month or two. Just grab a decent card (or use on from current build) to get by till the 9900GTX comes out (expected june or july but not 100%) because one of them is gonna be insane. And then when that comes out you can just sell the old card, or hang onto it incase something breaks...or use it for physics processing like Nvidia is always talking about (though im pretty sure that doesn't actually work in a game yet does it?) And if you can actually wait till the 9900gtx comes out to get the whole thing even better since other parts may have gone down in price by then.
One more thing, If you are building this mostly for gaming and are planning to overclock a dual-core chip is probably a better bet. The 8400 seems to be the best chip out there for overclocking and since most games (99.999999%) don't use more than two cores, hell most don't even use two, you'll be fine.
And trust me, two cores is plenty to work with for pretty much everything. with my e6750 OC'd to 4GHz I can rip and transcode a DVD while watching a DVD while surfing the net while updating a bunch of my programs all at the same time.
Also, like the guy above im not too big on EVGA or Corsair...i prefer XFX and OCZ.
Although i did just remember one thing about EVGA, if you buy a card now and the 9900gtx comes out you can go through their "step-up" program where you give them your old card and pay the difference, but this only works for one card I think, I don't believe you could trade two 9800gtx's towards a 9900gtx but you may be able two, you might wanna check with them.
My bigget concern is... are their any games out there that actually use a x2 8800GTS SLi to its full compacity? Like I stated before, the 8800GTS and the 9800GTX have nearly identical benchmarks.
Now that I said which OS ill be using (Vista Ultimate 64 Bit), is x2 4G kits (8G total) worth it? Even as a saftey net for future gaming. What im currently looking at is Age of Conan, Warhammer Online and ive been wanting to try Crysis but I want to make sure that the rig I build can take it. By take it it mean: 1680 X 1050 with all the settings cranked as high as they can go, including the AA and such.
It'll take care of everything but what you want out of crysis....though it'll almost be there in crysis it just won't quite make it. I seriously suggest you consider waiting a while for the 9900gtx, they will be expensive but since you were thinking 2x 9800GTX its not much of a difference for what is finally spose to be a big jump in performance....the first card worthy of the "9" as the first digit in the number....also they will be launching a 9900gts at the same time...will be a bit cheaper and should still be better than your other options