I have a singer 111W155 and 211 (dual needles) and they are beasts. 5-8 layers of denim/canvas is nothing to these machines.
I would recommend a sailrite machine as they have very good resale value over getting an old industrial machine and paying to have it tuned up and buying a servo motor.
Some tips on buying:
Always see the machine SEW not just RUN. Most industrial sewing machine mechanics are gonna charge $100+ an hour + parts. If you are mechanically inclined you can time it/fix it if manuals/parts lists are available.
Get a machine with at least 1/2 lift
Walking feet/needle feed/alternating feet.. at least one, preferably several if you do many layers (like 4+).
Reverse (but I would not pass up a good/cheap machine if it did not have it)
SERVO MOTOR!! Industrial machines run at 3000 stitches per minute. Much to fast for detailed/complex work or a novice.
Just buy a table.. they are like $100. Don't make one. A good table/work surface pays for itself with better results.
