Buying a CPU is more important than buying a graphics card. If you feel you should go with the Xeon than that is what you should buy.
However, you could get away with an i5 and save about $60, maybe. As they are more than enough for gaming, and should be more than enough for gaming for the next three to five years, in which case you will probably buy a new computer, anyways.
A single cpu can last the life of your PC if it's researched properly, and the Xeon you listed is good enough to last you a long while, yet.
By the way, the Xeon you mentioned is about 15% less powerful than the 4790, and about 25% less powerful than the 4790k without any overclocking.