The PC that was in use has been said to be a 4690 (that's a Haswell "refresh" Core i5) with a GTX 980. That's what will get you high settings at 1920x1080, 30fps, apparently. So the rumors that the game chews up and spits out GPUs have some foundation.
We don't know whether the CPU is limiting, but an FX-4300 is pretty far down the list of high-performing CPUs, somewhat more than half of the "minimum" Core i5 2500k. However, if you have a motherboard that takes an AMD FX, you can upgrade within AMD and still get a high-performing CPU on the same motherboard, for a lot less money. Watch compatibility of specific models when upgrading, as some motherboards cannot handle the high power demand of some of the FX-8xxx CPUs.
The 660Ti is quite a bit stronger than the stated minimum 660, it should compare well to anything less than a 770 or 970.
So I would be reluctant to upgrade the CPU at this point, because we don't know whether it would be limiting. If I did upgrade, I would consider an AMD FX-8xxx first. I would be reluctant to upgrade the GPU, because you already have a high-performing GPU. I would see how the game performed for me and see whether anybody comes up with good bargains in hardware to get high performance out of the game.
We know you can throw a lot of money at the game and get something that will play it well. We don't know how little you can get by with and play it well. When you have a good starting point and money is tight, I would want to know the latter (how little you can get by with) before spending hard-earned money.
