Don't worry about diggles numbers, they are made up. (some are, others are correct.) Look at my previous posts, the GTS250 and GTX460 BOTH have a TDP of 150W. The GTX460 is probably a bit underrated as it has two 6pin plugs. Each of these plugs can supply 75W of power, or 150 in this case. Keep in mind that the PCIe slot itself can supply 75W as well, so it has up to 225W available to it. I doubt it uses much more then the 150W, but if they only gave it one PCIe plug you wouldn't be able to OC it very far. The important thing is that if they both require ~150W, they should both need the same amount of power. Its stupid to claim one needs 32A and the other needs 26. 6A * 12V = 72W, or one less PCIe plug. Notice however he claims the one needing more power is the one with one less plug. (as a side note I've told him his figures are off, but he usually responds with insults, etc so I've gave up talking to him.)
So, back on subject. Its mostly correct that your bill doesn't depend on the PSU. It gets a bit tricky however and you need to start looking at the real world. Most PSUs are most efficient at around 60-75%. Above and before this amount and the efficiency will go down. For example, if you have a PSU that is rated 80+ bronze, then it needs to be 82%, 85%, 82% efficient at 20%, 50%, and 100% load. This means if you have a 700W PSU, it will be most efficient at providing around 350-400W of power. If you have a 500W PSU however, it will be most efficient at providing 250-300W of power. The trick is to know how much power your system will need max and get one that can do it, and then find a PSU that is most efficient at the load your computer will be in most of the time. The easiest thing to do is to simply get one that will handle your system at load. The difference between 80%, 82%, and 85% in dollars per year doesn't amount to much.
just wondering, what will happen if my PSU, got the required watts for a GPU but the 12V rail is not enough? like for example: a generic 500W PSU with a single 12V:19A handles a GT240 that needs a 12V current w/ 25A.
First off, a GT240 doesn't need 25A. The GT240 doesn't have any PCIe 6 pin plugs, so its maximum draw is limited to what it can get from the board, 75W. 75W / 12V = ~6A. A GT240 needs about 6A of 12V power to run. Even if you had one of those 125W CPUs, thats only another 10A. (we are up to 16A if you need help with the math.) Boards and drives don't need 9A, trust me on that that. Most GT240s would be paired with a lower end CPU, but even if you used one of those big 125W CPUs anything that can do 18-20A will be fine.
To answer the question, if you buy a PSU that has enough wattage but not enough amperage on the 12V rail, you'll have power problems. The CPU and/or GPU might throttle their clock speeds, causing lower then expected performance. Your computer might run ok, but when high electrical demands are placed on it it might just trip the protection circuits in the PSU (assuming they are there) and you'll have reboot or shutdown issues while gaming. Last, if those Over Current Protect (OCP) protection circuits aren't there or are set up incorrectly, it could cause the PSU to "blow up" taking who knows what with it. Yes, its as bad as it sounds.
If I HAD to pick from that list, I'd get the FSP. You only need around 300W, probably less then that. The rails were stable up to that point. If you can find something better then post here so we can confirm. Good luck with your build.
Edit: Forgot the link to the 80+ wiki page.
http://en.wikipedia.org/wiki/80_PLUS