Inline undersink water filter

I am interested in having one of your Doulton ceramic systems installed in my kitchen undersink. I'd like it to be an in-line system so I don't have to have an additional tap on my countertop. Is this possible?

We receive same request as yours every now and then which we recommend our Regent I which have high capacity and flow rate with Imperial Ultracarb Cartridge It is only available from us and the cost is $249.00 without the faucet and install hardware. For more details visit the following link: http://www.doultonusa.com/doulton_water_filters/Imperial-high-flowrate-RegentI.htm

What install hardware do I need with this setup? also, does this system provide maximum filtration?

Your cold water shut-off valve is most likely located in the center back of the sink base cabinet, You want to install the filter closer to the cabinet door as you may need to clean the ceramic cartridge every now and then as well periodic change out.
We can give you 3-4 feet of 3/8" PE tubing for the filter supply. On the shut-off valve end you'll need a 3/8" plastic compression tube ring (delrin) and a 3/8" compression nut (use the existing if you can) to attache the filter supply and the other end of the supply simply push in into the filter inlet (build in push-fit inlet/outlet).
For the filter outlet to the faucet you'll need standard 3/8" faucet riser of appropriate length (gray plastic riser). All the items you need are commonly found at local "big box" or hardware stores. Should you need any elbows to avoid sharp bends (kinks) we can supply you with push-fit elbow (s) at no charge. Push-fit connection instructions are supplied withe the filter. The Imperial Ultracarb filter efficiency is same as with our slimline Ultracarb element.
Push-fit instructions can be found on the following link: http://www.doultonusa.com/Instructions.htm