как узнать требуемую мощность для видеокарты?

105 ватт

ATI Radeon HD 3870 and ATI Radeon HD 3850 System Requirements
PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard
450 Watt or greater power supply with 75 Watt 6-pin PCI Express® power connector recommended (550 Watt and two 6-pin connectors for dual ATI CrossFireX™)
Certified power supplies are recommended. Refer to http://support.amd.com/us/certified/power-supplies/Pages/listing.aspx for a list of Certified products
1GB of system memory recommended
Installation software requires an optical drive
DVD playback requires DVD drive
Blu-ray™ / HD DVD playback requires a Blu-ray / HD DVD drive
For a complete ATI CrossFireX™ system, additional ATI Radeon™ HD 3800 series graphics card(s), an ATI CrossFireX Ready motherboard and one ATI CrossFireX Bridge Interconnect cable per board (included) are required

Warranty does not cover damages to this product caused by overclocking

ATI Radeon™ HD graphics chips have numerous features integrated into the processor itself (e.g., HDCP, HDMI, etc.). Third parties manufacturing products based on, or incorporating ATI Radeon HD graphics chips, may choose to enable some or all of these features. If a particular feature is important to you, please inquire of the manufacturer if a particular product supports this feature. In addition, some features or technologies may require you to purchase additional components in order to make full use of them (e.g. a Blu-Ray or HD-DVD drive, HDCP-ready monitor, etc.).

©2010, Advanced Micro Devices, Inc. AMD, the AMD Arrow logo, ATI, the ATI logo, Catalyst, CrossFireX, Radeon and combinations thereof, are trademarks of Advanced Micro Devices, Inc. Other names are for informational purposes only and may be trademarks of their respective owners.

450 ватт бп требуется для этой видео. Только качественных а не за 800 рублей.