Alright, your CPU multiplier is probably locked by the CPU. That's why they make the Black Editions: the multiplier is unlocked so it's a lot easier to overclock. Raising the FSB will increase both the CPU and RAM frequency. The RAM divider, depending on your bios, will either show you a ratio like 1:1 or 1:2, or simply show speeds like 667mhz or 800mhz. If you set it to 667 but raise the FSB, it can still end up running at over 800mhz depending on how much you raised the FSB. I don't know the exact relationship off the top of my head because it's a little different with Intel and AMD CPUs (I think?) and I've been so busy with school that I really haven't had time to do anything new with any of my stuff for quite some time.
So no, the divider is not the same thing as the CPU multiplier. The divider will allow you to up your FSB without making your RAM run too fast. Depending on how good the RAM is, you might be able to get it running around 800mhz or a little higher after the overclock, but you might have to sacrifice some as well depending on if you're trying to max out the CPU or try to find a stable combination (which, if you sacrifice some ram speed, you could possibly tighten up the timings a little to compensate).
Hope that made sense.... gotta get back to studying now lol
BTW if you boot to a memtest disk after you overclock, it should tell you exactly what frequency the ram is running at. I'd probably do a little more searching so you can at least get a good guess of where to start with the divider so you don't end up getting an unbootable system and not knowing how far over you went.