Under sink water filter/purifier?

Anyone have or have info regarding a water puifier and or filtration system that is plumbed into the kitchen sink on a seperate faucet? I'm looking. For a really good unit that will filter/purify against bacteria, giardia, crypto, VOC, possibly viruses, etc. Maybe with two filters and a UV light. It's for an apartment, so space is a consideration. Budget is flexible, but not unlimited. Google is yielding mostly manufacturers' sites. Kitchen installations seller is suggesting Aqusana AQ 4601 unit. I will get to the library to check out Consumer Reports, but your input would be appreciated.

We filter our drinking/cooking water with a multi-stage filter from Culligan. It has a carbon filter and a reverse osmosis filter, and several more specific filter cartridges in series. They know what needs to be filtered in your general area and taylor the specific filters to the pollutants present. The flow rate is good and the company comes out once a year to replace the cartridges at no extra charge. The system comes with a high quality faucet which goes in the spray hole of your sink, or they can drill a hole for it. The system also purifies the water for our ice cube maker. We lease the system for $32/mo. We have it mounted on the wall in the laundry room, but I think it could be squeezed into the space under the sink.

I suggest an RO unit. It will take out just about everything except dissolved gases.

They can be had for <$150 at the big stores.

Virtually all of them include sediment and carbon filtration as well.

Check out the system sold through AMWAY. It uses UV and can be used below the sink through it's own sink top dispenser or can be countertop and hooks directly to the faucet.

I bought a RO system from this site:

http://purewaterexpress.com/

Sato's customer service is top notch- when I had some leakage after changing filters this year, he helped me track down what the problem was by email. On New Year's Day.

I got the Slimline II model HTF-101 from Hydrotech, but the new quick-change model looks really slick.

One big difference between this and the ones you get at the big box stores is how the membrane works. The big box ones have membranes that need chlorine, but they only last a year. The ones from this site have chlorine sensitive ones, so it needs a carbon filter in front of the RO filter. But the membrane lasts 3-5 years.

I bought an RO system with a 5 gallon tank under the sink. Works great. No more 16.9oz bottles. No more nasty tap taste. Cost about $200 with install, requires an annual filter change of around $100

Thanx to all for you input. I'm still considering the possibilities.