Someone help me build ~850 High performance pc

http://pcpartpicker.com/p/A8W0
This will be about the best you can get for 850$. You'll be able to play BF3 on high at more then 60FPS but not ultra, and with the AMD 8 core CPU you can edit and render very well with out any hold ups.
7950 Benchmarks of BF3: http://www.tomshardware.com/reviews/radeon-hd-7950-over...

Will you need to buy a monitor and OS?

monitor yes, but OS no and i am not including that in the pc budget

thanks man

just curious what would 950 do for me and this time without the OS

Don't get cheap coolmax psus, they're terrible, if you have about 950, my suggestion :

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3570K 3.4GHz Quad-Core Processor ($219.99 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($33.24 @ Amazon)
Motherboard: ASRock Z77 Pro3 ATX LGA1155 Motherboard ($87.55 @ Newegg)
Memory: Crucial Ballistix Sport 8GB (2 x 4GB) DDR3-1600 Memory ($43.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($69.99 @ Amazon)
Video Card: EVGA GeForce GTX 670 2GB Video Card ($359.99 @ Newegg)
Case: Cooler Master HAF 912 ATX Mid Tower Case ($39.99 @ Newegg)
Power Supply: Antec Neo Eco 620W 80 PLUS Certified ATX12V / EPS12V Power Supply ($29.99 @ Newegg)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($16.99 @ Newegg)
Total: $885.72
(Prices include shipping, taxes, and discounts when available.)

For video editing, nvidia cards are better, if you want to lower the price get a 660 ti : http://pcpartpicker.com/part/asus-video-card-gtx660tidc...

Good for a strict gaming build, but video editing will require more than 8 gb of RAM, and depending on the Editing software, it may not be able to use 8 cores. You're giving him a build before asking enough questions.

What video editing software will you be using? This also affects the choice of video card, as some are optimized for AMD, and other are more optimized for Nvidia's CUDA.

premiere after effects and photoshop

Nvidia cards are better for that, 8GB of ram is fine, you can always bump the ram for 16GB if you need.
This ram has a combo with 670 gtx evga or 660 ti asus : http://pcpartpicker.com/part/gskill-memory-f312800cl10d...

Here is an great build for editing and with still be able to play BF3 and high at a constant 60FPS. You can either get the GTX 670, which will be about 10% better fir editing, but the Radeon HD 7950 will be a bit better in most games and is about 5% better. Personally I would go with this build with the 7950 because the i7 being hyperthreaded will preform much better with editing and will pick up the slack of the AMD GPU.
http://pcpartpicker.com/p/Abb1

I strongly disagree with the RAM comment here. In a video editing machine, the amount of RAM is nearly as important as the CPU. You want enough RAM to be able to store the entire video file you're working on (as well as revisions) in system memory, and they can get considerably larger than 8gb, especially since you want to edit HD video. 16gb is the minimum I would put in a new video editing machine at this budget.

Don't buy RAM seperately for this machine. RAM from two seperate kits is fine for a gaming machine, but when you're working on a project, you want stability, which is better when all RAM is from the same kit.

The latency of the RAM in also more important to a video editing machine than it is to a gaming machine. Getting a 16gb set of CAS 8 RAM is worth the extra ~$15 over CAS9 for editing.

for video editing, it's best to buy all your RAM at once, in a single kit.

http://www.build-my-home-computer.com/build-video-editi...

enjoy!