I did a similar setup with a Craftsman Shop vac and the vortex. I added a bag inside the craftsman to help catch the fine particles and sears also sells a muffler for around $12 and that keeps the sound down.
One thing the Festoolvac does that is not available on the craftsman is to allow you to control suction when using certain tools like a sander. I found this vac handle at lowes.
The red band rotates to cover an opening. With this simple arrangement you can have some control over the amount of suction.