Upgrading, need opinions

[GodofCats]

I'm trying to do two things in the next few days. Upgrade my computer AND build a new computer with the leftover parts for my aunt...

Here is my system as of now:
1.6GHz Dual Core Intel E1200 CPU
2GB of DDR2 PC6400 RAM
1GB ATI Radeon HD3650 video card
Gigabyte socket 775 Motherboard (its pretty decent for what it is)
150 SATA HDD
2x DVDRW SATA drives
550 Watt PSU, this is kind of a lower end one

Here is what I plan to buy for just me:

MSI Core i7 motherboard, $190
http://www.newegg.com/Product/Produc...82E16813130221

ATI Radeon HD4870 video card, $190
http://www.newegg.com/Product/Produc...82E16814102801

Corsair 850 Watt PSU, $130
http://www.newegg.com/Product/Produc...82E16817139009

6GB DDR3 PC10666 RAM, $89
http://www.newegg.com/Product/Produc...82E16820145220

I already have the Core i7 920 CPU, bought it for $230 at a local computer store... I'll also be buying my aunt a cheap $35 HDD from newegg and a $25 case from newegg or said computer store... I do high end gaming and have a little under $700 for a spending limit. Any suggestions? I am wondering if I should go with a higher end motherboard, but the thing is I'm pretty much at my limit for $$. My aunt might give me a $35 for the Hard Drive, but other than that I am on my own. I do the highest end of Real time strategy gaming, and I don't want this upgrade to miss a beat. Well anyways, please let me know if you have any suggestions. Thanks.

[tomtoon]

Looks good.
You can lower the PSU to a corsair 650w:

http://www.newegg.com/Product/Produc...corsair%20650w

And for windows to utilize and recognize more than 3.25GB RAM, you need a 64-BIT O.S

If you want to go vista, choose this one:
http://www.newegg.com/Product/Produc...82E16832116488