The e5430 is essentially a Core2Quad. It was a fine chip, but it's quite old now. You would have to get an old server or professional workstation to get one.
It really comes down to what your budget is. If you can get the e5430 for free or very cheap, it could be very inexpensive to upgrade into a cheap gaming rig. Of course the i5 will perform much better and is should still be fairly inexpensive.
You should be considering a lot of other factors for gaming: is the Power Supply able to handle a Graphics Card (GPU)? Does the pc come with a GPU or will you purchase one separately? Does the case even have room for upgrades?