http://channel.tomshardware.com/2007/11/27/sbm_price_performance/
Just follow the guides - it's not hard to build one for less than $1000 using very nice parts.  Assuming that you'll never play the game at higher than 1280x1024 resolution you REALLY don't need the biggest baddest video card(s) top play it either... just something that isn't 4 or 5 years old ;)

Minimum System Requirements

    • Windows XP SP2 or Windows Vista
    • 2.0+ GHZ Single Core Processor
    • 512 Mbytes of System RAM
    • NVIDIA 6200+ or ATI Radeon 9600+ Video Card
    • 8 GB of Free Hard Drive Space 


Recommended System Requirements

    • 2.4+ GHZ Dual Core Processor
    • 1 GBytes of System RAM
    • NVIDIA 7800GTX+ or ATI x1300+ Video Card
    • 8 GB of Free Hard Drive Space

http://dfbgaming.com/Thread6433.html &lt;- you know you want to :)