1300 - 1400 System Build, First time! Help?

Hey, I'm going with a AMD build. I have a couple questions though. Do i need a 800Watt to power all of this? Is that too much? Too Little? Is the Biostar TForceTA790GX good with the Phenom 9950? Would i be able to fit my PCI-E TV Tuner with the big 4870x2 Graphics on that MOBO. Which MOBO should i use?? Any advice on the whole system would be appreciated. This is my first build.

LITE-ON 20X DVD±R DVD Burner Black IDE Model DH-20A4P-04 - OEM
Item #: N82E16827106228

Western Digital Caviar GP WD5000AACS 500GB 5400 to 7200 RPM SATA 3.0Gb/s Hard Drive - OEM
Item #: N82E16822136149

XION Supernova XON-800R14N 800W ATX12V / EPS12V SLI Certified CrossFire Ready Modular Power Supply - Retail

Microsoft Windows Vista Home Premium SP1 64-bit English for System Builders 1pk DSP OEI DVD - OEM
Item #: N82E16832116488

Sunbeam CR-CCTF 120mm "Core Contact Freezer" CPU Cooler - Retail
Item #: N82E16835207004

NZXT TEMPEST Crafted Series CS-NT-TEM-B Black Steel / Plastic ATX Mid Tower Computer Case - Retail
Item #: N82E16811146047
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Skytek 52usbreadwrite2.0 52-in-1 USB 2.0 Card Reader - Retail - COMBO

BIOSTAR TFORCE TA790GX A2+ AM2+/AM2 AMD 790GX HDMI ATX AMD Motherboard - Retail
Item #: N82E16813138128
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AMD Phenom 9950 2.6GHz Socket AM2+ 125W Quad-Core Black Edition Processor Model HD995ZXAGHBOX - Retail - COMBO

VisionTek 900250 Radeon HD 4870 X2 2GB 512-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
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CORSAIR 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model TWIN2X4096-6400C5 - Retail - COMBO

Hauppauge WinTV-HVR 1800 MCE Kit 1128 PCI-Express x1 Interface - Retail
Item #: N82E16815116015

Total - 1361.91 Budget is $1400 /w Mail in rebate its 1281.91
Thanks again!

I heard that the 4870 x2 is so big and with the Biostar having the PCI-E x1 slot right next to the video card slot..that its high possible that the TV Tuner won't fit..