Pat,
I have a TenHigh 6040 50W laser cutter, bought from Amazon. It can cut at least 1/4" ply.
It's the best investment in hobby tooling that I have made, closely followed by my 3D printer and mini-lathe.
If you get one of the cheaper cutters, plan on changing the lens to get a much better quality and more highly focused cut.
I use K40 Whisperer as the controlling software, as what comes with the laser is worthless.
Paul