Which will help handle my game at full

i've been saving for a new gaming computer for a while, i think the time to buy is now. so far i've picked out

Intel® Core™ 2 Duo E8400 3.00GHz 6MB Cache 1333MHz FSB
4GB« Dual Channel DDR2 SDRAM at 800MHz - 2 x 2048MB
Killer K1 Gaming Network Interface Card

but am stumped about my graphics card. all i really play is WoW, but i'd like to play it at full graphics. i thought about dual 9800GT 512MB , but a friend told me a single one would be over-kill for that, but i found i can can get the dual 9800 for the same price as a GTX 260 896MB. so my question is, is a single 512MB 9800 over-kill/good enough or should i go with the GTX 260.

i do play fable and fallout 3, but am not worried about those on full graphics.

Hello and Welcome to DEV

The system your thinking of looks good
If you could tell us your total buget..we could help you better.
Personally I would go for the EVGA GTX 260 (Core 216) or you can go for a ATI counter Part HD 4870.(For Future Proofing)
Yes they are a bit overkill for WOW...but you never know what will come out in the near future that you might want to play.
I have the Intel Xeon E3110 (brother to the E8400) and a EVGA 8800GT,and I can play any game out there.
The reason I go with Nivia or EVGA,is because of there lifetime warranty.
You don't mention a Power Supply..... I would put more thought into that than I would the Killer K1 Gaming Network Interface Card
Only because I've read mixed reveiws...I think it depends more on your Internet connection than anything else.
And PSU are SO overlooked by most people...you want to look at amps on the 12 volt rail rather than total wattage.
If your PSU has 700 watts and 40 amps it won't be as good as a PSU with 600 watts and 50 amps.
If you LOOK HERE you'll be able to figure out what size you need as far as PSU's go.
As far as names
Seasonic
Antec
Enermax Liberty
Fortron (FSP Group)
OCZ
PC Power & Cooling
Silverstone
Tagan
Sparkle
Are really good

well for a total system build, you would be wise to avoid LGA 775 a bit, simply because the socket is being replaced and basically the processors available now are pretty much what will be available until it is completely phased out. My advise would be to wait for Core i5, or go on the more cost effective side of LGA 775 as you wont have much of an upgrade path with that socket a year or so down the line. As for memory, 4gb is ideal but you may want to go for DDR2 1066 considering it only carries a small price premium. The killer K1 NIC is great, but honestly your not gunna get more than gadget appeal out of it. It wont give you much more performance and though packet prioritizing will improve your ping, its going to do very little to improve lag if the server or your connection is the bottleneck. My advise, put that $150 towards something that can really pay off, such as a nice big monitor.

And on that note of the monitor, brings us nicely to the video cards. Your monitor is going to be the biggest factor in determining what video card you should use, as higher resolutions will require more graphics power than lower resolutions. If you are running 1680x1050 or anything lower, the 9800 GT is going to be a great choice. For 1680x1050, a single 9800 GT will be plenty power for all the games listed to run smoothly on high details, perhaps even with some AA/AF and other eye candy knocked up. For anything higher however, such as 1920x1080/1920x1200, you would be wise to look towards cards like the GTX260 or HD 4850. As you can see here the GTX 260 is in a higher class, and is really going to be ideal for higher resolutions because of that extra power. It will be overkill for anything lower, but like I said, if you wanna put that killer NIC money into something that can improve your gaming experience, you can get 24" LCDs that do 1920x1080/1920x1200 for about $300 these days, of course they will scale upwards from there until you reach that golden 30" LCD pushing 2560x1600...but at that point you're looking at $999 entry level

For WOW specifically anything here is going to be more than you really NEED, but as a guy who has built many gaming rigs for WOW players, I can tell you that they never regret investing big in displays, higher resolutions mean you can have more on the screen, and its much easier to manage your HUD. If you really want some fun you could look into dual or triple displays, but be prepared to spend about $600+ just on the graphics sub system, then figure another $100-$150 per display So really, you'll have to think about what monitor these cards would be paired with before one becomes a better option than the other.

as a total for budget, i was willing to spend no more then $2,000.

my power supply spec are
Type ATX 12V 2.0

Continuous Power 750 Watts

Active PFC Yes

Efficiency >80%

Output +5V @ 16A
+12V1 @ 18A
+12V2 @ 18A
+12V3 @ 18A
+12V4 @ 16A
+3.3V @ 30A
-12V @ .2A
+5VFP @ 3A

Protection Thermal Fan (w/speed control)
Over Voltage Protection
Over Current Protection
Short Circuit Protection
No Load Operation
Auto Restart

i'm still looking at displays, i'd love a 30" but like you said, i'll be hurting a little from it. and after taking the cost from the killer k1 out of the equation, it does allow a higher budget for something bigger then the 20" i was unhappily going to settle with.

after cutting the killer k1 cost and going for the GTX 260 i'm at a total of $1,530 (no monitor either) my biggest problem with my budget right now is that i am (military) stationed over seas and would have to pay for shipping and handling which no one can seem to make cheap. and you say the GTX 260 will handle 1920 x 1200 display fine?