I5 or i7 for CPU-intensive, non-multicore scientific simulation

Hi,

I've been thinking about building a desktop for a few months now (right now all I have is a laptop). I have learned a bit in my journey, but I've also found that my computer needs seem to differ from many other people's computer needs. I want a powerful CPU that I can overclock, but I am not going to run any applications that make heavy use of multiple cores; I will never have more than two video cards (and probably won't have more than one any time soon); and I will never play the latest video games.

What I need is a CPU that will give me the best bang for the buck when running simple C programs that diagonalize matrices and solve partial differential equations and other number crunching stuff like that. FLOPS is what I care about - not game performance, not 3D rendering performance, not Winzip or Winrar performance.

I am looking at Intel CPUs and the obvious contenders that everyone continually recommends right now are the i7-920, i7-860 and i5-750. I know that the general consensus is that the 920 is the best. But for what I'm doing - running CPU intensive programs that don't use multiple cores - is there any real reason to get the 920 or 860 versus the 750?

i5-750 with a Gigabyte P55 UD4P for $373 versus i7-920 with a Gigabyte EX58 UD3R for $478.

That's a $105 that I don't want to spend if it's not going to be translated into a real performance difference in applications that are meaningful to me (the simple C ones I write and compile with Dev-C++, or at most science programs like BOINC / World Community Grid).

Can anyone set me straight here? Whatever I buy, I'm go to try to OC it as much as possible. I know the big ol' 920 kicks everything's ass, but will it kick ass where I care about it? That $105 could easily go toward better cooling, better graphics cards, food, etc.

Sorry for asking an over-asked question. I'm really only asking because I'm not using my computer for big games or graphics apps like it seems most other people building powerful computers are.