Ok, update:

I searched in eBay, and there are a lot of filters out there... thankfully, there are a couple for under $100. But I see two main distinctions,
FILTER type1 --> Reverse Osmosis
FILTER type2 --> RO + De-Ionized Filter

Any ideas? Will type1 work fine? Better question: Will type2 be the best?

I thank you for your help

-turtle420

PS: I started building my cabinet today!!! Had to stop because of the rain... I'll be back tomorrow