Budget AMD pc build

Good day folks, I've been out of the PC game for a while now (current system Athlon 3200+ on Abit UL8 w/ GF4 Ti4200) but it now has some issues. Well, it has 1 major issue. It won't boot. My 500W Thermaltake PS is from 2001 and has never had a day off.
What I'm looking at is : (all in $CAD)

AMD Phenom II X3 720 2.8 GHz SKT AM3 L2 1.5MB $147.77
GIGABYTE AMD770 DDR3 AM3 SATA PCI-E $96.77
SAPPHIRE 100265L Radeon HD 4830 512MB 256-bit GDDR3 $99.77
OCZ DDR3 PC3-10666 Gold 4GB Dual Channel Kit $99.77
OCZ ModXStream Pro 700W Power Supply $79.77

I've got a new Samsung DVD drive and a WD Blue Caviar 320Gb HD ready to go into it.

My concern is I've gone WAY overkill on my RAM and that I could also go down to the 550BE phenom. But I figured I won't be upgrading for several years again so it should last.
My PC is currently used for downloading, video conversion, internet; but I would like to edit the HD videos from our new camera. Right now I can't even play them smoothly.

Do I have an OK build or could scale it down even further. I'm sure regardless of what I do it will be a MASSIVE improvement.

change that 4830 to a 4770 or a 4850

As said above probably upgrade your GFX card with the money you could save on a smaller PSU. 4GB would be overkill on XP but would probably do you for Vista or Win7.

how about the Athlon II X4? Have you considered that as an option?

Go with a nice Athlon 2 X2 dual core. Get a quad later when they are cheaper and better.

Use the savings to get a better graphics card, I highly recommend you wait for a nice 40nm 57XX series.

As far as the psu goes, people are saying its overkill, its really not. The OCZ modstream is one of OCZ's cheaper inflated wattage psu's.

Put it this way, it has 2- 25a rails. My OCZ Fatality 550w has 2- 25a rails as well.

if you are going to edit HD videos get the Athlon II X4 due to the fact that it'll get the job done faster and better. It may have no L3 cache but the recent THG review it seems you don't need that L3 cache as it only makes the CPU faster by about 10%-15% somthing you won't notice.