Advice on my planned new system

I am planning to build my first computer from scratch and I'd like to get some feedback on the components I selected. It's the first time I'm doing this, so any help is greatly appreciated!

I am working a lot with Photoshop, other Adobe products and especially I need a computer that can handle AVCHD video. Usually I don't play games.

I heard that Intel's i7 handles video encoding the best, but it's out of my budget. So I went with the following components:

CPU: AMD Phenom II x4 955
Motherboard: ASUS M4A 78T-E AM3 790GX
Ram: G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)
Case: Rosewill Blackbone Black Steel / Plastic ATX Mid Tower Computer Case
Power supply: Antec BP550 Plus 550W Continuous Power ATX12V V2.2 Modular Active PFC Power Supply
HDD: Western Digital Caviar Black WD6401AALS 640GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

I calculated, it would cost me about $600, which is probably the max. for me.

I'm going to reuse an old CD/DVD drive and at least for now I'm not going to get a graphics card, since I'm not planning on playing games.
Are the on-board graphics sufficient?

Does anyone have experience with these components? Do they work together well? Am I going to be fine with 550W power supply? Anything else I need to consider?

Any other comments welcome.

Thanks for the help!