The i7's only take DDR3 800/1066 ram and the i5's take DDR3-1066/1333 ram so it appears that the i5's got the advantage, but the i7's have 4 cores with 8 threads and the i5's have 2 or 4 cores with 4 threads which gives the edge to the i7's i would think. The i7's also have 3 memory channels while the i5's are 2 channels and yet again the i7 wins. Im trying to figure out which would be better for me? I want to build a really fast workhorse to be used for trading. I also want to be able to run multiple apps(mostly trading apps and excel.) Lots of data is going to be processed continuously and i will be optimizing trading systems with multiple inputs. Sometimes calculations can take hours to run. I might play some games down the road and I also will be running about 8 monitors. Also, just as a reference which i5 with 6gb of DDR3-1333 running with it would actually be comparable to a i7-930 with 6gb of DDR3-1066?
You forgot to mention that i'7 9** CPU's have a tripple channel memory controller. Because the relatively high launch price of the i5 - you would be better off buying the i7 920.
the 760s only $205, and since P55 Mobos are cheaper it saves him $100+ easily without losing much performance, Triple channel RAM doe nothing except in special applications like rendering or video editing.