Which rails power individual components / good PSU for this build?

So Im trying to figure out which rails different components of a system operate on. I've read through alot of different forums and reference guides on the subject but seem to be getting mixed information about which components run on which rail of a PSU.

Ultimately my goal is to be able to understand how to determine which power supply i shoudl get for a build I am working on. BTW...this is my first build (obviously).

Here are teh components I plan on using with estimated power consumption:
- EVGA 680i LT (100W)
- EVGA 8800 GT OC (225W)
- Intel Q6600 OCed ~3.2 GHz ~1.5V (125W?)
- 2 x 1GB DDR2 800MHz (worrying about OCing RAM when i get OCing CPU understood better)
- 1 Optical DVD writer/reader
- 1 WD Caviar SATA II 7,200 RPM
- Antec 900 Case w/5 x 120mm and 1 x 200mm fans
- I havnt decided which CPU cooler to use yet...but im expecting for it to be around $50 and be appropriate.

Ive checked out my estimated power consumption using multiple calculators and im looking at ~500W power consumption while at full load.

As it is I was looking at getting the OCZ Game XStream 700W max PSU which rails look like:

AC INPUT 115V/230V - 60/50Hz
DC OUTPUT +3.3V +5V +12V +12V -12V -5V +5VSB
Watts 36A 40A 18A 18A 0.5A - 2.0A

My specific questions are:
1. Which rails do the mobo, video card, hard drives, optical drives, case fans, and etc operate off of? I'm pretty sure alot of this depends on when the component was made and each component can be different. I've even seen different listings for Intel and AMD architectures. I'm really looking at current tech levels and where current products stand now.

2. Does my estimated power consumption look accurate? Will this PSU be appropriate? If not, what woudl be a good suggestion for ~$100? (This all relates to question one in a sense, but a little redundancy never hurts :)

3. By my estimations if I add another 8800 GT I will need about 650W from my PSU...will I be cutting it too close with this PSU?

I understand this whole thing should prob be in the system build section but since my main question revloves around understanding which rails im dealing with when determining which PSU is right for a certain build i felt it was appropriate for this category :)
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More about which rails power individual components good build
  1. Sorry if this is a double post...I;m just trying to understand how this works and I think I have been getting a little confused from mixed information via different sites and what not.
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