Re: General overclocking question
Overclocking the i7 to 4 GHz or higher is helpful if you're doing a lot of constant intense processing on it, but for gaming and basic use it won't make a difference (as your CPU is already idling most of the time during these tasks). However, for compiling, rendering, multitasking, Folding@home, or other intensive processing applications overclocking will make a very noticeable difference. If it is capable of using 100% CPU then it will be noticeable. Also the CPU can use the RAM at however fast it is going. If you overclock the CPU and the RAM together the whole system will work better. This is generally how you do it as most overclocking involves raising the base clock (BCLK) or front-side bus (FSB). Raising this frequency affects nearly everything in your PC. To get the device clock you multiply the FSB or BCLK (depending on the system, Intel i series systems use BCLK, everything else uses FSB) by the device's multiplier (your CPU has a multiplier listed in the specifications, your RAM also has one set by the motherboard).
I got my 930 to 4.1GHz and it performs better on Folding@Home, a distributed computing project that studies protein folding. It can sometimes be considered a benchmark as people usually run it to compete their systems against others (for instance, on a forum like this) but Folding@Home uses a much more real-world computation system than most synthetic benchmarks and is probably a bit harder on RAM.
Other things where you would see improvement is program and 3d environment compiling, video editing, photo editing, 3d CPU rendering (as many professional level 3d apps do), and heavy multitasking. You also have more CPU room to run virtual systems using VirtualBox, VMWare, etc.