For some ideas on what can be achieved with your budget see my post #18 @ http://www.geekstogo...ve/page__st__15
Some further guidance;
You should not decide on a PSU until all other components are confirmed, this will allow you to use a PSU calculator such as this example http://www2.corsair.com/psufinder/
which will help ensure that you have enough clean and stable power;
For the best and most stable performance you should where possible purchase a CPU and Ram that have been tested and approved by the motherboard manufacturer, this is referred to as the QVL ( qualified vendors list ) understand though that there are too many products released for them all to be tested so other hardware will be compatible but not proven to be.
I don`t see an OS such as Windows 7 on your list, if you need to purchase W7 it will add circa $100 to your build costs, see canned speech below which is intended to ensure new builders are aware of the legal implications of using licenced products;
Just a cautionary note, unless your OS disk is the full retail edition you cannot use it with a new MB as an OEM disk is tied to the original MB it was paired with, to use an OEM disk with a new MB is software piracy and therefore illegal.
Exceptions to the above are 1: If your MB is replaced under warranty and 2: If your MB is replaced out of warranty with an alternative type but same brand due to the original model no longer being available, an upgraded MB however will require the purchase of a new OS licence.
Do you have any components to bring to your build such as a screen, DVD/CD drive, keyboard, mouse etc.