Unless you have at least some experience in kitchen layout and design, you're probably going to be much happier having a real person involved (like HD) to help you figure it out. This is something you're going to live with for a long time and if the layout doesn't work, you'll regret it daily.
Look for solid plywood boxes, dovetailed drawer fronts (the drawer backs are not as critical), solid wood face frames and doors, and good quality hinges and drawer slides.
There's nothing wrong with buying online to save a few bucks, but don't skimp on the quality.
