We used Everpure - You can get from Amazon.

We're very pleased with the Multipure Aquaversa we put in a few years ago. The filter gets replaced once a year.

http://www.multipure.com/store/aquaversa-below-sink.html

I've been really happy with this one from costco http://www.costco.com/Premier-UF3-3-stage-Ultra-Filtration-System.product.11487220.html 

We have an older model of the one quadesl linked, under the kitchen sink. It works fine.

After much research, we've decided to go with the aquaversa.

We use a Bodyglove under-sink filter and the price has gone up SO much every year! Almost $400 now for the canister we paid under $200 four and a half years ago. They've gotcha.