You want to buy a premade cabinet is what I'm hearing. Just go with the box store cheapos, and modify anything you may want different.
I make all my own single box cabinets to each size I need, screw them together and use www.maplecraftusa.com
for the doors.They also sell the whole cabinets like you asked.
I buy sheets of 3/4 plywood or melamine for the sides and half inch for the backs. Some wood screws and putty and send out the measurements for the doors, or make your own doors out of plywood and some iron on edgebanding for the edges.
The options for building them yourself are the best, custom fits always work best.
I like the habitat route also, or look on craigslist or post an add in the wanted on craigslist, but be careful of who you respond to.