I am trying to build a budget gaming computer and I don't know what CPU I should get. I have been looking at the phenom because it is cheaper but I have heard that the i5 was much better. I plan on running higher end games.
Also if it matters the video card I am running is an AMD Radeon HD 6870.
You should spend the extra money and definitely get the i7 2500k along with a cheap aftermarket heatsink. Just an average overclock on the 2500k could yield 30-40% more performance, since you could easily get to 4.5ghz from 3.3ghz.
The 2500k is also about 40% faster than the Phenom II clock for clock, and the PHII can only reach about 4ghz with a cheap aftermarket, so the performance is definitely better.
You will only have to upgrade the graphics card for future games(it works well right now), the i5 will last for quite a long time at the rate things are going.