I'm not the best guru when it comes to windows boxes, but I can certainly chime in about where you're looking to purchase a box from. Server Matrix would be my recommendation for the best company. As you've probably already seen the pricing there is pretty competitive and affordable for those of us who are looking to run with the smallest budget one can run on. The staff there has been great when I've needed their help on certain issues. They tend to be a little slow on some issues that are less important, but if you have a problem they work for you in a fast and well informed manner.

I had the 'pleasure' one night of server troubles that were related to what turned out to be a tough fix. I don't remember exactly what the issue was at this point, but I do remember SM being helpful and doing their job.