Just in case some of you have confusion about the 12v dual rail, here's what I know about it (though I'm far from an expert and would appreciate it if people would correct any inaccuracies in this):
Scenario 1 (Single Rail):
33A at 12v
This means that you can plug tons of things into that 12v rail until you reach the limit of 33A. However, ever single time you plug a single thing into that rail (depending on how much juice it sucks), your PSU is likely to drop the voltage a tad. For example, when very little juice is being pulled, the rail may be at 12.5v when pulling 5A total (this may be a bit high, I'm exagerating these numbers so don't take them as truth but just see the patern). Plug in a single video card and it may be down to 12.1v when pulling 16A total. Plug in a second video card and it may be down to 11.8v when pulling 25A. Add a DVD burner and while burning let's say you're pulling 30A, you might be down to 11.5v. See the pattern? Again, some numbers are a bit exagerated but you get the idea.
Scenario 2 (Dual Rails):
18A at 12v #1
16A at 12v #2
This means that the CPU has rail #1 all to itself. Typically expect your CPU to pull 10A or less so this rail has plenty of power to spare that, unfortunately, nothing else in your system can use. Despite my "unfortunately", this is good for CPU stability and with that CPU overclocking. Rail #2, now, is used to power everything else in your computer. Motherboard, video cards, hard drives, DVD burners, etc.
Do not be fooled into thinking that a PSU with a dual-rail can be thought of as practically the same as a single-rail PSU where the amps or sum of amps are the same. In this case, 18A + 16A does not equal 34A. You would be better off with the 34A single rail.
Another piece of info about the new ATX2.01 standard is that it states that none of the 12v rails should constantly be over about 70% load. That means that you should not be consistantly pulling more than 70% of that 16A. So that means you now only have 11.2A that you can pull nonstop before you begin declining the lifetime of the PSU (according to the standard).
Last piece of advice: I have no personal experience with dual rail PSUs. This is all based on the research I have done on them. I just purchased my first dual-rail PSU yesterday and have yet to put it in a system.
Hope this helps with any confusion.
-Jax