It is impossible to say what is reasonable to expect from your particular cpu at a certain voltage because they are all different.
Dont worry about the memory bandwidth for now. That is in the more advanced parts of the guide. Have a read of the first part of the guide that is based on the P5B, it should fill in any gaps, as the P5K guide assumes that you have read the first part
Dont be scared of adding voltage to the NB, I have been running this at full whack since day one, and the same for the P5B's before it. All you need to do, is make sure that there is some airflow through the case, and youll be fine.
Same with the CPU voltage, dont be scared of adding it in small notches, just keep an eye on the temps.
So, in a nutshell, dont worry about too many things at once while you are learning, and see how high your cpu will go at temps that are acceptable for your cooling, and once you settle on an overclock that is good for you, THEN you can go and mess around with the RAM and timings/speeds