Budget Build HTPC / Photo Editing- Buying this Weekend, Input Please

Value your input on my proposed build- it will be my first / hope to build for under $550. Have the CPU, buying the rest of the items this weekend. The system will be used for watching movies / internet, music, some photo editing (PhotoShop and Coral Paintshop Pro) and occassional video editing using Pinnacle Studio software. The system will be in a living room entertainment center / very limited space. Cool, quiet and low power consumption all considerations.

Look forward to your opinion / thanks for rating the build.

Already own:
AMD Phenom II X4 805 CPU, 6 MB total cache, AM3 ($79.00)
Existing DVD-CDRW Combo Drive, Lightscribe
Existing 46" LCT TV 1080p
Wireless keyboard and mouse

Need to purchase:
COOLER MASTER Elite 360 RC-360-KKN1-GP Black Steel / Plastic ATX Mini Tower Computer Case - Retail ($32.00)

Western Digital Caviar Black WD6401AALS 640GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive - OEM ($74.99)

G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Dual Channel Kit Desktop Memory Model F3-10666CL8D-4GBHK ($84.99)

COOLER MASTER Silent Pro 600 RS-600-AMBA-D3 600W ATX12V V2.3 SLI Certified CrossFire Ready 80 PLUS Certified Modular Active HD ($79.99)

GIGABYTE GA-MA785GMT-UD2H AM3 AMD 785G HDMI Micro ATX AMD Motherboard - Retail ($89.99) ALSO considering GIGABYTE GA-MA770T-UD3P AM3 AMD 770 ATX AMD Motherboard ($79.99) which would be paired with a discrete graphics card that I would buy now rather than later

Heat sink and fan for CPU - undecided on the brand/model, welcome recommendations for the X4 805 CPU (CPU came without the heat sink and fan)


Will add either now or later:
Radeon 4850 1GB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card / OR the 4870 (currently both are over $100)
Blu-Ray Player Retail version (currently about $100)

daship, thanks for the feedback.

In terms of motherboard / video combo, based on your experience, what are your thoughts about the gigabyte board with the built in graphics (785G chipset) and forgoing the discrete card? This would also cut down the Power Supply needs as well.