I have no idea where your buying these parts from but your paying way too much for them. This is of course i am right in assuming you live in the U.S and not Canada (which if you are would explain why the prices are so high). Your part list is good so i'm going to redo your list with cheaper updated prices and show you your savings and what to do with that savings.
Processor
Get the E6850 instead. You can get it at that same price your paying for the E6750.
Intel E6850 CORE 2 DUO E6750/ 3.0GHz/ 4MB CACHE/ 1333FSB/ LGA775
$285 (Note: Go to ZipZoomFly.com to get it at this price)
Motherboard
Gigabyte GA-P35-DS3P P35, ATX, FSB1333, 2xPCIE, SATA2, RAID, 1394, GbLAN, DualBIOS+
$159 @ NewEgg.com
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128047&Tpk=GA-P35-DS3P%2bP35
Graphics Card
Sapphire ATI RADEON™ HD 2600XT
$145 @ NewEgg.com
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102102
Memory
Corsair 2GB TWIN2X2048-6400C4 (2x XMS2 1GB) Twin2X PC-6400 DDR2 RAM, 2x240-pin DIMMs
$159 @ NewEgg.com
$123 @ ZipZoomFly.com
http://www.newegg.com/Product/Product.aspx?Item=N82E16820145034&Tpk=TWIN2X2048-6400C4
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=85025-6
Hard Drive
Seagate ST3320620AS 3.5INC CUDA7200.10 320GB 7200RPM 16MB SATAII NCQ
$80 @ NewEgg.com
http://www.newegg.com/Product/Product.aspx?Item=N82E16822148140&Tpk=ST3320620AS
(Note: At the price you were gonna pay you literally could have gotten a 500GB Western Digital drive at $110)
Optical Device
PIONEER DVR-212 8x/ 18x Dual/ Single Unbranded Beige OEM SATA
$63 (X2)
Keyboard/Mouse
LOGITECH Cordless Desktop EX 110 USB/ PS2
$57
Operating System
MICROSOFT WINDOWS VISTA HOME PREM 32BIT DVD DSP OEM
$112 @ NewEgg.com
http://www.newegg.com/Product/Product.aspx?Item=N82E16832116202
Old List Total Cost: $1312
New List Total Cost: $1024
Savings: $288
Now i'd take that $288 savings, NOT get that ATI card and use that cash combined with the savings to get you a 8800GTS 640MB card instead which smokes that ATI like a limp cigar.