You could drop to an intel e5200, they run about $50 and you won't see much difference (plus they OC like cheetos crunch!) You could go with a smaller HDD, the 320Gb go for about $50. The last place I'd rob from would be the GPU. You can get a decent one for $50-60 but that's the place you are most likely to see a significant difference.
So wth these changes + dropping the monitor you are looking at about $200 in savings. At that price point an AMD build or even a prebuilt might give you a better value.