Wow, cabinetry is my specialty and the terms pre-fab and custom can mean one thing to some people and a completely different to others. I prefer to use the term "Stock" meaning produced with no modification from the manufacturers specifications and "semi custom" for some modifications allowed with possible upcharges and then "custom" which typically means every cabinet is produced per your specific requests. Factory finishes can be on all three types of cabinets with varying degree of expertise. A factory finish is not necessarily a bad thing at all-typically can have excellent durability and the conditions are well controled helping to keep a consistent finished product from one cabinet to another and especially if you need to order a replacement cabinet down the line. Cabinets bought off the store shelf would still be considered "stock" as are cabinets ordered from the manufacturer- you just might get a better selection of finishes, door styles and cabinet options. You could also use a local "cabinetmaker" and get stock cabinets as they may order there boxes broken down and ready to build from an outside vendor and then "customize" then at your home. Best advice I can offer is make sure you inspect any cabinet product before ordering-not just the door style and finish the whole cabinet box . That way you will get the best product you can that satisfies your desire for quality.