Thanks. So what you're saying is I should try and find a compromise between the 3 settings to get the best result. Any suggestions though?
Correct. If less noise and faster shutter speed are what you are after (in a darkened environment), then you need to think about a "faster" lens (ie one that can make use of a wider aperture).
If the widest your lens can currently open up to is f/4, then switching to an f/2.8 would allow the lens to let in twice as much light, letting you double the shutter speed (allowing you to freeze camera shake and subject motion), or halve the ISO sensitivity (potentially reducing grain or noise).
Being able to open up to f/2 would let in twice again more light, or 4 times that of f/4. And so on with f/1.4 and f/1.
The progreassion (taken from this article:
http://en.wikipedia.org/wiki/F-number)
is:
f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128
Each 'higher' f-stop in this progression lets in half as much light as the one 'lower', and each 'lower' f-stop lets in twice as much light as the one 'higher'.