Excalibur, people I know think they "know about computers," and I know how much you hate people like that. For added motivation, they like Antec cases. Basically, I want you to write a complete rip of their system compared to mine, which you helped build most of.
Theirs: http://secure.newegg.com/WishList/PublicWishDetail.aspx?WishListNumber=15879048
Mine: http://secure.newegg.com/WishList/PublicWishDetail.aspx?WishListNumber=17630447

They also forgot a monitor and cd drive.. They also claim DDR2 is superior to DDR3 in every way.

(: have fun.

What if you don't need a monitor or CD drive? o_0

All I can say is that for an extra $150, Ex's build gets you a monitor, an OS, better memory (unless I am very confused) and a CD drive. The 2nd seems much more money-efficient. Ex might not be interested in writing a rip, though.

Nvidia graphics card

I've never had any problems with mine.

GeForce GTX 260 - AHAHAHAHA. it's 2010. GDDR5. Also, it's slightly faster than a 4870, which is $70 cheaper. The $200 range has a big gap in ATi's cards (2 4850s outperform it, but it requires Crossfire), so you either spend $150 on a 4870/5770 or $300 on a 5850. 5830 sucks.
q9400 - AHAHAHAHAHA
Caviar Blue 640 - Why bother with the blue when you can get a black? $15 is either a lot, or a little. At $900, don't be trying to save $15.
Antec 750W - holy hell. $120 for 350 W more than you need. It's not even a seasonic. Modular is nice and all, but really not all that worthwhile.
G.Skill 4 GB kit - Lol 5-5-5-15. At least get 4-4-4-12 @ 800 MHz.
Antec 900 - waste of money. If you spend $100 on a case, I think it should at least have SOME aluminum in it.
Corsair hydro - Internal water cooling has its benefits, but this thing is quiet, ricer, and cools to +20 C on low. It's also $20 cheaper. Go get a caviar black with it.
Asus p5n-d - First off I'm guilty of the same thing: I got an SLI board on a single card. But seriously. Why would you do that?

There's a few things that are good about nVidia graphics:
CUDA - much better support than stream. Also tripcuda
Drivers - Let's face it, ATi's drivers suck, and linux support is terrible
PhysX - I have no idea what this really does, but hey, whatever
Hybrid SLI - I can only assume they have a better implementation than hybrid crossfire, which is terrible.
None of these would convince me to get a non-ATi card, unless I got a heck of a deal.

The 2 4850s are pretty much top tier, beating out even a single 5870, which costs $430, vs $210 for the dual cards. Of course, you have to spend an extra $50 on a good PSU, and probably more for the power bill.

I would have gotten those if they were out when I built my computer. Unfortunately, and I swear it's a rule for me, something better and cheaper always comes out right after I buy whatever it is I bought. I dunno if ATI has this yet but I noticed that there are some 3D settings for my 8800GTs. Dunno if that's worth anything as I haven't used it and I'm too lazy to figure it out, but it's there. I think my cards were $180 bucks when I bought them, I'd say they were worth it, dunno about any of the new ones.

This is a separate processing unit which computes very detailed physics. Only supported by a few games though. Mirror's Edge makes good use of it.
Afaik it takes a huge bit off of your cpu load for games that have PhysX.