I like the small form factor of the MicroATX machines and I don't run stuff that is too intensive. I just want a good system that will last me a few years. This is what I put together using NewEgg. One of the upgrades I'm thinking of is moving to a 5670 gard instead of the 4670 for the faster memory. That would still keep me under $800.
What exactly are you trying to use the computer for? We could help more if you followed the guidelines from the link in my signature...
Here's a very basic suggetion:
HDD: WD is slower, louder, hotter and more expensive than the newer 500 GB platter drives out there. Pick up the Samsung Spinpoint F3 500 GB (or 1 TB for less than 2 500 GBs) or the Seagate 7200.12 in the same size.
PSU: There are better units out there. You should really get a unit that is at least 80+ Certified (Corsair 550W for $85 after rebate or Seasonic 550W for $74). There is one 80+ Silver 550W unit (OCZ Z Series) for $80 after rebate). These would not only be higher quality, but would also lower the power bill, generate less heat and likely last longer.
Suggestions if this is for use as an HTPC:
GPU: Definitely pick up one of the 5xxx series cards. They run a lot cooler than the older ones.
CPU: Look into some of the cheaper, lower wattage CPUs, such as the X4 925. This would lower the heat in the unit and make it quieter. You wouldn't lose enough performance to be noticeable. You could even drop down further to a X4 620 or a X3 425.
CPU: Drop to a X3 425 to save about $100.
GPU: Get the HD 5770. Then use what's left in the budget to get a dual PCIe 2.0 (8x/8x) board and a slightly bigger PSU.
I included an opsys also..... W7 pro vs premium for added benefits... my preference but getting premium would save about $30.
I chose a tri core vs quad.... slightly lower cost.... duals are not enough for me and you may run into that problem too.
The mother board has on board video. It may be enough for you. If not chose the card you want. I have a tough time buying inexpensive video cards because my demands are greater than yours.