If I am not mistaken, your 403A had 9 stitches including the straight stitch. You can definitely do the Stupendous Stitching class with that machine. You won't have all the decorative stitches that CAW uses, but you can do lots with what you have.
I took the class when it first came out and only had my old Brother VX560 machine which had a total of 9 stitches plus straight stitch and buttonhole stitch. I used the various utility stitches and modified the length and width to get some neat effects. I enjoyed the class so much that I made several pieces on that machine.
Once I decided that I liked using the techniques she showed, I bought a Brother PC420PRW from Amazon.com for under $400 including shipping. That was 4 years ago. You can now get them for even cheaper. That machine has a couple of hundred stitches. You do not need an embroidery machine, nor do you need a machine costing thousands of dollars. For even less you can get some of the Brother machines that do decorative stitches but have a relatively small throat space. Check out Walmart etc.
I have recently had a show of my work in a local art gallery. All of the pieces used similar techniques to those taught in Stupendous stitching and were made either on my VX560 (9 stitches only) or on my PC420PRW. I also did some free motion quilting and bobbin work on a couple of the larger pieces on my PQ1500s (straight stitch only). I was lucky enough to sell some work and also to have another gallery owner to invite me to put some work in his commercial gallery. So you see, you don't need an expensive machine to successfully do the techniques that CAW teaches in Stupendous Stitching.
Rob