" when i try L4D at that res it sucks. no matter what cpu i use it sucks."
That's because your weak graphics card is the bottleneck even at that low resolution. A 9400gt just won't cut it for l4d.
We would have to talk about a graphics card upgrade to a 4670 or 4850. We can discuss this more if you are interested but I see money is tight right now.
Yes I would use the quad core. It's better for source games anyway.
