I guess most ppl ask me this question. First, it would be strange for me to recommend a specific brand, as this is going to look like commercial stunt which i largely disagree with.
Mostly i recommend products from USA for one strong reason, they have laws and policies to ensure that such products meets a strict standard. Read up on this site, American Water Works Association and you will gain some understanding of the mentality and policies they have : http://www.awwa.org/
But here are the guidelines :-
1. MasterFilter - You will only use the master filter to filter out dirt and rust. Some master filters even claim to filter chlorine but in most cases you only need a master filter to filter the dirt. Additional claims are mostly either unjustifiable marketing claims (eg master filter filtering chemicals up to xxxx microns etc). Look, the master filter have to handled large volume and pressure, it just doesnt have the mechanics to handle other more fine grain filtering.
I would say products from pentair (http://www.pentair.com/) or waterco (http://www.waterco.com.my/) should be good and decent. There are many other products
2. Inhouse Water filter -
If really want to spend and dont mind spending, i guess the Amway water filter is a safe choice, be prepared to pay ^_^. Actually if you boil water, you get the same result as what the Amway ultraviolet component does, it kills bacterias...minus the cost. But on the whole, at least Amway is honest in their claims. (if they reduce the price to say RM 1200, and the filters to 50%, i would say it would be the appropriate value).
Do a google search on water filter products from USA and i believe you will find many have distributors in Malaysia that you can contact and evaluate for yourself. If the product dont comes from USA, at least make sure its sellable in USA.
What water filter products i use? Apart from the experimentation products of the twin combo filter in my wet kitchen, i do use a a main water filter at my dry kitchen. Well lets just say its the same water filter u will find in "Old town kopitiam", "gloria jeans", "MCDonald", "StarBucks" and onboard of AirForce one (^_^). Its called Everpure (http://www.everpure.com/)
However let me warn you, the filter comes in 3 parts (the poly dirt filter, the carbon chlorine filter and the Everpure filter), the most important is the 3rd one which is direct import from USA, the first 2 component the local distributor here created it themselves for "profit" and the name on the label is very much misleading that you would think all 3 component comes from USA. I think they called it "EverGood" or something. (duh!). If you already havve master filter, just buy the third component.
Anyway, well, so far the quality is constant and i do get crystal clear and it filters even chemical (certain lethal, cancerous ones). It is NSF certified for 2 claims which i have verified and happy with. Its also cheaper than diamond/nesh which is uncertified and full of misleading claims.
Now dont get me wrong here, Diamond and Nesh DOES filter water. I am not saying that they dont do anything. I am saying they don't do a LOT of those things they claimed in their marketing material (watch the video http://malaysiawater.blogspot.com/2007/06/diamond-energy-water-hong-kong-reaction.html ). They do not filter any dangerous chemicals (no certification on this), and they sure dont filter the bacterias (no certification). If you boil the water, then i guess all is fine ^_^.
Basically, a RM 150-200 panasonic filter will get you the same if not better results. In fact if you already have a master filter, those pensonic/panasonic filter is all you need.
**** Sept 2009 : There is a new water filter by philips, that uses UV and the double filter (sediment, carbon) and priced at just rm 1200. Definitely a better buy than Amway. The NSF certification is also true.