Alright, I came up with a couple of options that I thought might work.
It assumes that you'll be reusing your monitor and peripherals from your old computer.
Option 1- more of a kit (somewhere around $550 after rebates):
The barebones
A case and PSU
Windows
Optical Drive
You could reuse your DVD or get a different case/psu combo if you wanted. I'm a little leery of the PSU in the combo if you later decide to get a big video card as an upgrade, but it should be fine with the kit mentioned.
Option 2 - more mix and match (about $625 after rebates):
Windows
Optical Drive
CPU/MOBO combo
RAM/GPU combo
PSU/Hard Drive combo
Case
With this option, you could reuse your old DVD to shave off $20 ish and buy a cheaper case (or get one locally) if you needed to cut down more.
Option 2 is generally better stuff - same mobo and CPU, but the video card is a good bit better and you get double the RAM. You will have less HDD space, but it will be faster a faster HDD, and you could add in your old HDD one as a second drive if you need more space. If you're planning on gaming with more modern 3D games (shooters and such), I'd think the extra money was worth it, and I believe that the GPU comes with a free copy of DIRT3 if that's your thing.
But if you're mainly building for something like Star Ruler, which is more CPU bound, both should be effectively equal, and it might be better to save a bit now, and then save up for a really good video card if you needed/wanted one later. Plus option 2 has a lot of rebates, so your initial price will probably be more like 700 and you'll have to wait months to get the rebates back, which can be a pain.
Anyways, hope it gives some ideas if nothing else.