I am working on building my rig and I'm now to the power supply. I have an Antec 900 case.

I will only have one video card and most likely will not overclock the CPU or GPU. I will most likely get an ATI 4870 or Navida GT200 (9900 GT, GTS, GTX?????). I most likely get two hard drives and four gigabytes of DDR2 800 memory.

I will most likely will also get a 600-700 watt power supply with at least 50 amps on a single 12V rail.

Most of the power supplies I have looked over are ATX 12V version 2.2 but I see the newest version is 2.3. Is there much of a difference between the two versions? I've looked up these standards but have not be able to find much information other than it complies with new Intel and AMD standards, but what are these standards? Will a version 2.2 power supply run a quad core CPU later on when I upgrade from a dual core CPU?

I see some recomendations here for cheaper and very pricey power supplies but what about something in the middle. I want to spend about $125 or less. This is the one I'm looking at now: http://www.newegg.com/Product/Product.aspx?Item=N82E16817139005. Thank you for your help.

Bitbrain:

I will only have one video card and most likely will not overclock the CPU or GPU. I will most likely get an ATI 4870 or Navida GT200 (9900 GT, GTS, GTX?????). I most likely get two hard drives and four gigabytes of DDR2 800 memory.

I will most likely will also get a 600-700 watt power supply with at least 50 amps on a single 12V rail.

Most of the power supplies I have looked over are ATX 12V version 2.2 but I see the newest version is 2.3. Is there much of a difference between the two versions?

There is not much of a difference, Bitbrain. Most likely you will want to read HERE.