I am definitely more editor then computer builder, but since you are targeting the 7D as your primary footage, is 8 GB of memory and no raid system going to handicap your abilities? Im sure others with expereince in building systems will have more to contribute.
Avid DS / PrP / After Effects Editor
Mac Pro 3,1
2 x 3.2 ghz Quad Core Intel Xeon
Nvidia Quadro 4000
24 gigs ram
Maxx Digital / Areca 8tb. raid
2 hard drives is the minimum... 3 is better... when the price comes down again... plus, you don't need such a large drive for boot & software
My 3 hard drives are configured as...
1 - 320Gig Boot for Win7 64bit Pro and all program installs
2 - 320Gig data for Win7 swap file and video project files
When I create a project on #2 drive, the various work files follow,
so my boot drive is not used for the media cache folder and files
3 - 1Terabyte data for all video files... input & output files (*)
(*) for 4 drives, drive 3 all source files & drive 4 all output files
Search Microsoft to find out how to redirect your Windows swap file
8Gig ram is OK... 16Gig is better when you have funds... have you looked at CS5 Benchmark http://ppbm5.com/ site?
For future drive & ram additions, you might want to consider an 850w power supply... 750 may be OK, but for my similar computer I have an 850w PS http://forums.adobe.com/thread/652694 and LOTS of case fans
Welcome to the forum. One of the first things you should do is to do a search before you post a question. In most cases, you will find an answer to your question. I've posted this to 4 separate "What do I build questions" this week alone.
Here is your parts list from Newegg. You will toss another $100 or so in cables and fans, etc.
Motherboard: ASUS P8P67 DELUXE (REV 3.0) LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS: $209.00
Processor:Intel Core i7-2600K Sandy Bridge 3.4GHz (3.8GHz Turbo Boost) LGA 1155 95W Quad-Core Desktop Processor Intel HD Graphics 3000 BX80623I72600K: $320.00
RAM:G.SKILL Ripjaws X Series 16GB (4 x 4GB) 240-Pin DDR3 SDRAM DDR3 2133 (PC3 17000) Desktop Memory Model F3-17000CL11Q-16GBXL:$150.00
NVidia GTX570: EVGA 012-P3-1571-KR GeForce GTX 570 HD w/Display-Port (Fermi) 1280MB 320-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card: $340.00
HARD DRIVES (5): HITACHI Deskstar 7K1000.D HDS721010DLE630 (0F13180) 1TB 7200 RPM 32MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive. $130 EACH OR $650.00
CASE: COOLER MASTER HAF 932: $140.00
POWER SUPPLY: Antec EarthWatts Series EA-750 Green 750W ATX12V v2.3 SLI Certified CrossFire Certified 80 PLUS BRONZE Certified Active PFC Continuous Power Supply: $100.00
BLURAY BURNER: LG Black 12X BD-R 2X BD-RE 16X DVD+R 12X DVD-RAM 10X BD-ROM 4MB Cache SATA Internal 12X Super Multi Blue with 3D Playback Blu-ray Disc Rewriter WH12LS38 LightScribe Support - OEM: $70.00
I trust this helps.