Upgrading my PSU.

Hello, I am upgrading my graphics card from a Radeon HD 6850 1GB to a Radeon HD 7950 3GB, and I am also getting a new monitor (BenQ RL2450HT), and my power supply I have now is 600W, though I feel like it is a piece of junk because it makes grinding/vibrating noises; it's a Diablotek PSU that I got from Tiger Direct.

Here are my specs/what they will be in a week or so:
GPU: Sapphire Radeon HD 7950 3GB
CPU: AMD Phenom II X4 960T 3.7GHz (O/C)
Motherboard: ECS "horrible stuff" AM3 6GB/s
RAM: G.SKILL Sniper 8GB (2x4GB) 1333
PSU: Diablotek 600W
HDD: 500GB 7200RPM 64MB Cache 3GB/s or 6GB/s (I can't remember, though I think it was a Seagate)
Monitor: BenQ RL2450HT
Case: NZXT Crafted Series Tempest 410

I am going to upgrade my PSU, I have $200 to spend, but I would prefer not spending all $200 as I am going to upgrade my motherboard next   Anyways, I am looking in the 700-800W range, I kind of want to be able to CrossFire eventually. So, my question is, how much wattage do you recommend, and what PSU specifically?

The ones I have in mind are:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://us.ncix.com/products/?sku=62224&vpn=P1750BNLG9&m...