Check out the P-6831 FX versus the P-171S FX.
The P-6831 FX is $1,349.99, and the P-171S FX is $1,599.99. As far as I can tell, the other other difference between these two machines is that the P-171S comes with the T7250 (2.00GHz, 800MHz FSB).
Are there any other differences? Is it...