My first build. Advice is welcome.

So yeah, as the title states; this is my first build. Since about mid-November I have been learning what I can from this site and others while picking and choosing hardware. Now that I have gained a decent understanding of what I'll be getting into I think I'm ready to purchase everything. But before I jump right in, I thought it be best to ask if everything is compatible, worth getting, etc. So enough chit chat, tell me what you think.

Case: Antec 1200
Motherboard: GIGABYTE GA-790FXTA-UD5
CPU:AMD Phenom II X4 965 Black Edition (125w or 140w?)
Memory: G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333
PSU: CORSAIR 850w (overkill?) Overkill it may be but I think I'm going to go with a 950w. It's only an extra $10.
GPU: SAPPHIRE Radeon HD 5770 (I will be getting a second later on)
Hard drive: Western Digital 640GB 7200RPM Now 1TB.
OS: Windows 7 Home Premium 64bit OEM (Should I get retail?)
Optical: LG Black 8X BD-ROM 16X DVD-ROM 40X CD-ROM LightScribe DVD±R DVD Burner

If you think I should make some changes let me know.

At first glance, I thought the 850w was overkill, but then I used this. Corsair PSU finder

If they don't have the exact part I use, I always go up. It suggested 850W minimum.

Also, on the western digital, are you looking at the black series? Double the cache for a little more. I think it looks good, well other than the AMD parts.

The hard disk is a bit on the smallish side. Why 640GB? Here's a 1TB WD Black for ~$20 more:

http://www.newegg.com/Product/Product.aspx?Item=N82E16822136337

OEM and Retail licenses differ slightly - OEM Windows licenses require that the software be sold with a piece of hardware. OEM tends to be a bit cheaper, too. This is why people will buy OEM software alongside a $2 SATA cable, because hey, it's technically hardware. In your case it won't matter, so long as that license stay with the machine forever.

Thanks for the help, guys. Now I just need to decide on the CPU, 125w or 140w. I know the 125w would be cooler but I don't want to have to flash the bios right off the bat.

i don't think you flash it if it's a revision of the same chip it probably has the same name family multi fsb settings. with oem licence, it's supposidly invalid if your motherboard fails or if you upgrade to a different motherboard (never really encountered this change, I think I have might be able to test this but not now) I had an oem machine that only boots(didn't try to install it) the restore disc if it was inserted into the original dvd rom drive that came with the system.