I'm trying to get fire extinguishers and I'm wondering whether I need to get a class K fire extinguisher if I already have an ABC fire extinguisher like this: http://www.amazon.com/Kidde-21005779-Fire-Extinguisher-160CI/dp/B000VBGG5Q
I've read somewhere that basically class K is more or less the same as class B but I want to see what the community says. :)
An ABC extinguisher should be safe for all three classes of fire. It may not be be the most effective possible choice, or the easiest to clean up after. Depending on what you think the hazards are, how willing you are to fight them, what experience you have, how badly you panic (as opposed to, for example, smothering the fire with a pot lid), and how much cleanup is going to aggravate you, a more specialized extinguisher may be a cheap and effective investment.
Anything that reduces hesitation, or time fetching the extinguisher, is a good thing.
As I understand it (from my yearly exposure to the Fire Chief explaining it, which in recent years added the "type K" extinguisher) those are really purely meant for commercial kitchens with built-in hood fire suppression systems - the type K material does not interact badly with the stuff used in the hood system while a normal ABC evidently does. The fire they are interested in (with that hood system the class K is supposed to work with) is almost exclusively a grease fire.
In your house/kitchen, an ABC is good, a bigger ABC is better, and an ABC you can get when you need one (i.e., have more than one in the house) is best - assuming the thing is in serviceable condition (green on the gauge, for typical home extinguishers.) Knowing you can also throw baking soda or salt on a kitchen fire can also be good to know - as is the lid trick already mentioned by @keshlam.
I'd add a CO2 BC rather than a Type K if I were adding something to that, myself, but that gets into personal opinion calls.
