Not RTA, but I've used the cheapest particle board cabinets from Lowes that I could get. We had them in our house for a few years before we built a bigger house, no complaints. I still have some of those in my barn as well and I have one spot on the edge where the laminate needs to be re-glued, otherwise they work fine for me. We replaced the ones in the previous house (turned it into her studio) recently with the more expensive Kitchenaid which have nicer drawer slides and adjustable hinges and shelves.
A caution on custom cabinets: We are not pleased with the custom cabinets we got but the contract was with the house builder and only says that he will provide cabinets. We went and talked with the cabinet builder and gave him drawings and internet pictures of what we wanted. Those were ignored. Dimensions of the cabinets were all wrong, the raised panels were not of the style we specified, and no ability to put in drawer pulls (?!?) but none of that was in writing. I suggest you have the custom cabinet builder actually build you a cabinet that has all the features you want (doors, drawers, trim, hinges, slides, etc) to see what you're going to get.