Will this do? (please help)

[spirit]

I will be getting this computer about two months from now so maybe the i7 will drop in price over that time.

Yes, I would imagine with the release of Ivy-Bridge, the Sandy-Bridge i7 2600s will fall in price... but so will the i5 2500s...

Also one of my friends told me that I have to check my memory so it is DIMM memory how do I do that

Buy desktop RAM and not laptop RAM (laptop RAM is SODIMM and the sticks are much shorter). The RAM you linked to is DIMM so stick with it.

Also what does the i7 have over i5?

The only differences as far as I know between an i5 2500 and an i7 2600 is that the i7 2600 has a slightly higher clockspeed (3.3GHz for the 2500 vs 3.4GHz for the 2600), the i7 2600 has 2MB more cache than the i5 2500 (6MB for the 2500 vs 8MB for the 2600) and the i7 2600 has hyper-threading which the i5 2500 does not have. In case you don't know, hyper-threading means that your Quad-Core i7 will actually have 2 threads per core, meaning that you will have 8 threads rather than the 4 threads that the i5 2500 has. If you don't need 8 threads, just stick with the i5 2500, otherwise, the i7 2600 is a good option. If you use multi-threaded applications then the i7 2600 is probably going to be the better choice, but if you don't use multi-threaded applications, stick with the i5 2500 and save the money, you'll save quite a lot.

The only difference between the i5 2300, 2400 and 2500 are the clockspeeds and the price, none of the quad-core i5 CPUs have hyper-threading.