I made my sewing table from two cabinets from Lowes; I think they were $39 each. Wood across top w/cut out for acrylic insert from Dreamworld, shelf below to support machine. On each side is a wood strip running the width of the cabinet so that it could be screwed into the particle board side of the cabinet - the back of the cabinet was too flimsy to hold it. So then the shelf is attached to those.
Maybe try some of that rubber shelf liner until you can work on your solution (which sounds like it should work). I think I've seen folks post that using that has helped. It's got a little bit of padding to it, that might absorb some of the vibration?