The Intel Core i7 930 would be a faster processor, but IMO would be too costly for a $900 budget.
If you live near a Micro Center, they sometimes sell Core i7 860s and 930s for $200, which is a bargain.
If you don't, I suggest this, if you do, replace the Core i5 750 with a Core i7 860:
Intel Core i5 750 2.66GHz - $199.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115215&cm_re=Core_i5_750-_-19-115-215-_-Product
ASUS P7P55D-E LX - $139.99 + $7.56 shipping
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131634&cm_re=asus_p7p55d-e-_-13-131-634-_-Product
G.Skill Ripjaws 4GB DDR3 1600MHz 7-8-7-20 - $114.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231303&cm_re=G.skill_ripjaws_4gb-_-20-231-303-_-Product
So far the total cost is $462.53.
A few more questions:
1) Will you be reusing your hard drives and case?
2) Would you like to add in another graphic card later?
3) What PSU do you have, which brand?
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1) If you said no to question one, then add these extras, otherwise just ignore this section:
Samsung Spinpoint F3 7200RPM 1TB - $89.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16822152185&Tpk=Samsung%20spinpoint%20f3%201tb
Cooler Master HAF 922 - $79.98 w/$10 rebate
http://www.newegg.com/Product/Product.aspx?Item=N82E16811119197&cm_re=haf_922-_-11-119-197-_-Product
Total is now $632.50.
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2) If you do not want to add in another card later, and prefer to just change the graphic card completely, ignore this post, otherwise
if you do want to add in another card, you should get this motherboard instead:
ASUS P7P55D-E Pro - $189.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131621&cm_re=asus_p7p55d-e_pro-_-13-131-621-_-Product
Add another $42.44 if you want to add in another graphic card later on, totalling to $674.94.
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3) If your PSU is generic, or came with the case, I suggest that you get the Corsair HX650W or TX650W if you would like to use two
graphic cards or keep your old PSU if you only want to use one. If you do want to add in another graphics card, you'll have to
go cheap a bit.
Corsair HX650W - $109.99 w/$10 rebate
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139012&Tpk=corsair%20hx%20650w
Corsair TX650W - $69.99 w/$20 rebate
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139005&Tpk=corsair%20tx%20650w
If you said no to question one, and no to question two, then the total cost so far would be $462.53
If you said no to question one, but yes to question two, then the total cost so far would be $614.96 (with the Corsair HX650W)
If you said yes to question one, but no to question two, then the cost so far is $632.50.
If you said yes to question one, and yes to question two, then you will be getting the Corsair TX650W with a cheaper graphics card for $744.93.
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The last section is the graphics card. I would go for the XFX Radeon HD 5850 for $318.49.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150477&cm_re=hd_5850-_-14-150-477-_-Product
Thus the total would be:
$781.02 if you reuse your old HDD and case, and do not want to add in another graphics card later.
$933.45 if you reuse your old HDD and case, but go for the add in a graphics card later option.
$950.99 if you decide to get a new HDD and case, but do not go for a graphics card later on.
If you want to add in another graphics card later, and want to get a new case and HDD, you'd have to get this graphic card to make sure you don't go too much over your budget:
PowerColour Radeon HD 5770 512MB for $129.99 w/$15 rebate
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131328&cm_re=hd_5770-_-14-131-328-_-Product
The total cost then would be $874.92, with one HD 5770, and it's ready for another one to be added in later, which will give HD 5870 performance in most games.