Here's what I would do. Spend the money for a better quality base coat, then purchase an inexpensive clear coat system. The problem with cheap single stage is the amount of coats necessary for good coverage. You WILL use a lot of material. This turns into a full day of painting as well as a ton of build up (mills). Couple that with a metallic color, and you will have a car that is zebra striped to hell and back. A quality base will cover quick and allow you to step back and see the finished product. BTW, use a "stabilized" base so you won't move the metallic when applying the clear.