First Build, $750 budget including monitor

[PoorGrad]

I'm a poor grad student looking to build my first desktop sometime in the next few weeks (unless it would be a lot better to wait until after the AMD Bulldozers are released). I want reliable components that will last at least 5 years, and I also want it to be upgradable. In fact, I'm considering building it in stages by only buying the necessary components (like starting with integrated graphics) and then adding to them throughout the next few months.

My usage expectations are:
- Moderate gaming
- Watching HD videos
- Moderate overclocking (I've never done it before, so I would like to be able to experiment with it)
- Virtualization (Running one GNU/Linux machine should suffice)
- Processor-intensive simulations (I'm a physics student, so I want to be able to test my simulations before submitting them to a computing grid)
- Light-traffic web server

This is all I've got so far:
- Processor: Intel i5-2500K will be nice for simulation and virtualization, and I can also experiment with overclocking
- Motherboard: A Z68 board would allow me to use the integrated processor graphics while I save up to buy a better graphics card. From the forum and the "Best Budget Poll" it sounds like some people like Asus and MSI, but generally Gigabyte is the way to go, though I'm not sure which one.
- RAM: 4GB should be plenty to start, but I want to make sure it works well with the mobo.
- Hard Drive: A reliable 1TB 7200rpm drive will probably be fine.
- Power Supply: It should be strong enough to support a solid GPU down the line.
- Case/Cooling: Since I plan to do some overclocking, I need something that can make sure the system stays cool enough.
- OS: Windows is expensive. I'm fine using GNU/Linux for a while (maybe hold out for Windows 8?)

Thank you for your advice!

 

[PoorGrad]

UPDATE: In order to take advantage of some seemingly incredible deals at Microcenter, I would like to build my system this week. I've narrowed down the motherboard to three options. One is bundled with the i5-2500K, so I will list the price as the difference between the bundle price and the i5 alone.

Gigabyte GA-Z68XP-UD3: $100 (no VGA output, HDMI only, would this be a problem using the processor as my primary graphics card?)
Asus P8Z68-V: $130
Gigabyte GA-Z68X-UD3H-B3: $145

I'm leaning strongly toward the Asus. It has a few bells and whistles that could be fun though unnecessary, but I like that it offers more flexibility with video outputs than the cheaper Gigabyte. The Asus also operates a 16-phase VRM as opposed to the 7-phase Gigabyte, which seems like it would offer improved stability. Any opinions?