Just my opinion from the info you have provided, I would most definatly go for the i3-540, it will probably give you far better performance than the AMD can and at the same price you cannot go wrong with the i3-540. Here is a comparison between the two: http://www.anandtech.com/bench/Product/143?vs=121
, they did not have the AMD 250 so I selected the 255(~100MHz faster than the AMD 250), but you can still see the huge performance difference.
Can you post some links to these PC's? One other thing I bet you there will be other PC deals on black friday online and at BB if you have one around you.