Get dual core. 2gb ram if you can, if not then I guess you could get by on a 1gb stick and upgrade when you have more money. To shave off a few bucks, you could drop the ram down to DDR2-667 or DDR2-533. Unless you're overclocking
, I doubt you'd notice a difference.
Like brinks said, that motherboard is the wrong socket type for that CPU. It's a 939, CPU's AM2. I'd stick with AM2. Heard this is a good budget AM2 board, but I have no experience with it.
You can get a better case for less since it looks like that one has an included psu (which probably sucks) and you're buying a separate PSU anyway. The CM Centurion 5 is a little cheaper, but not as flashy. I guess it depends on if you prefer the cheesy look
If you want to save a few bucks, this psu might be good enough for your system since nothing looks THAT power hungry. But then again, a bigger psu will give you more upgradeability, so it's up to you.
could also drop down to a x2 3800+ instead of the x2 4200+