I have considered adding a laser to my CNC but every time I get close to doing that I just send the file to my laser guy and he cuts it for me on one of his Epilog machines. One of these days I may add one, though.
The atom stack quad module is like $600. I'd skip that and get a 40W CO2 laser like a K40 instead. The problem with multipass laser cutting is it has diminishing returns and the cut quality will suffer. For 3/4" material, a CNC router is the way to go.Check out the AtomStack X20 Diode laser. It can cut 3/8" ply in one pass, so could probably do 3/4" in we or 4 passes. Atomstack.net It uses 4 lasers combined into one cutting area.