Wow-ed by the low price and seemingly amazing processors on these things, my friend and I both had this exact machine as our primary workstations up until about a year ago, and we both gave them up because no matter how much RAM we threw at them, they suffered from very odd and intermittent performance slowdowns that were almost impossible to determine the source of. I had an 8800GT video card, so it was definitely not due to a lack of GPU. I don't like to be so vague in my description of a problem, but I definitely believe there is some kind of performance bottleneck with this model...possibly due to the 800MHZ bus, or a lack of optimization for current OS versions. It also only supports SATA2, and has problems with lots of newer and larger drives (don't try to use a 3TB drive as your boot drive).
So with my experience in mind, I'd hate to see you drop a ton of money on this machine, only to potentially hit the same wall that I did. I currently have a dual-core 2.9GHZ i7 MacBook Pro, and performance is infinitely improved (something you wouldn't necessarily expect from a laptop, or considering the difference in processor cores).