The difference between the Intel® Core™ i5-2500 and the Intel Core i7-2600 comes down to 3 things. they are...
Intel Core i7-2600 has
-100MHz faster clock speed
-2MB more cache
In games these differences would make little difference but in some video edit you will see better performance with Intel Core i7-2600. Now unless you are looking for VT-d support you might want to think about getting a "K" processor to take advantage of its unlocked feature in the future.
for highly threaded work the i7 would be better, a quad is good for a while (3+ yrs?) in gaming circles. Consider a Z68 board and the 2500K, and apply a simple (and generally safe) overclock by raising the multiplier, and hopefully end up at around 4.2+Ghz