What power supply wattage to get?

What is the purpose of this build?

Also, PSU rated wattage doesn't matter much. What matters for a PSU is its +12V amperage because that's the power used by the graphics and CPU.

it for video editing and a bit of gaming

What graphics are you using and wouldn't a 16GB memory kit be better for video editing?

yea i think I may get the 16gb ram but I use the ati hd 5450 card, but I upgrade to better card in future

16 GB is recommended for i7 CPU's, you should go for 16GB minimum. I would also recommend just a newer graphics card, but not an expensive one. Just enough to get you through and be able to do things, such as a 650 or a 7770.

I'd also like to point out that your choice of RAM runs at 1.65v which puts alot of strain on Intel CPUs and voids your warranty.

what ram would you recomend?

I don't know where you're from so I'll assume US and use a Newegg link.

For your usage, I would suggest
G.SKILL Ares Series 16GB (2 x 8GB) 1600MHz

It's low profile, only 1.5v, and only 2 modules. Just right.

not sold in my country! damn! could you recomened a different ram please

it helps to know what country you are at . . .

new zealand, here use this website: pricespy.co.nz

You can use amazon, ram doesn't cost much to post, I believe I got my ram off Amazon for a good deal. and Im from AU

what about this ram: http://pricespy.co.nz/product.php?p=1221001
or should I go with corsiar vengence?

would this ram work in that mobo? http://www.corsair.com/vengeance-16gb-quad-channel-ddr3...

Corsair Vengeance works, yes. I don't really like 4 modules though.
Here,

http://www.ascent.co.nz/productspecification.aspx?ItemI...
http://www.ascent.co.nz/productspecification.aspx?ItemI...

Can you chose the graphics card that you want to upgrade to? Without knowing it, a PSU recommendation isn't easy. Or, you could give us a set amount of wattage to work with for graphics.

For example, 50-100W, 100-150W, 150W-200W, 200-300W, or any other range for a graphics card that you think you'd buy. I recommend either the first or the second, depending on how much gaming performance you want. The third or higher than it is for high-end gaming and you don't seem like you'd want to spend several hundred dollars on a graphics card.

Also, would you mind if we ask what software you'll be using in particular? I'd like to make sure if it is GPGPU acceleration-compatible. If it is, then you might benefit from getting a specific graphics card family more than the others.