GPU for Video Editing - No Gaming- What is BEST / Practical for this?

get a 4830/4850 with aftermarket heatsink to keep good temps and have your system running quiet.

Yes those cards are meant for gaming but with catalyst 8.12 drivers will use the card 640/800 stream processors (depending with card you choose) to do the video rendering for you. I wouldn't do with nvidia since you will have to pay for their cuda thing to use your graphic card to take the load off your cpu when converting videos

No you don't need 4870 with gddr5 because for video editing number of stream processors matters for raw computing power not memory speed so 4830/4850 would be good choice.

No sli/crossfire is meant for high definition gaming to split the graphic load between multiple gpus

No dont go high end if your only video editing, invest in quad core....core i7 920 would be nice with single 4850

I would recommend this card

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

4850 with passive cooler, less noise to worry about and my sapphire 4850 sounds gets annoying.

Lots of GTX 260's out there that look good for the price point of ~ 200 bucks. The ones with 192 stream processors are the ones at that price point. EVGA seems to have high build quality.

SLI/Crossfire.... I have no idea if they would help with this type of application. I know games have to be coded to use multi-GPU setups. I'm sure your apps would have to be specailly coded for that too.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

220 bucks... I thought I saw one like this cheaper.

Correct me if i'm wrong (usually am) you would be better for with a workstation card than a gaming card. Because workstation cards are made for video editing.

The 4850 sounds great. Great response. Thanks. In my other computer i use a GeForce 8800GT and it works very well for live playback of HD video timeline with effects un-rendered.

Its my understanding that A quadro workstation card (at under 300 bucks) would not be as powerful as the GeForce cards for similar costs. If money was not a factor i would get the Quadro 3500 or higher as they would outperform any of the GeForce series.

GEFORCE CARDS DO NOT SPEED UP ADOBE PREMIER!
Only the Quadro card series from Nvidia speeds up Premier, and they cost more than 1000 dollars.
The ATI 4000 series on the other hand, does accelerate Premier, as well as encoding, but from all I have scene dual cards, or dual chip cards will not provide additional acceleration from Adobe programs.