A little late to the party, but here goes. My car audio installation career utilized lots of 3/4 and 1" thick plexiglass(the brand) as well as lots of other acrylics. They are very dense and very brittle, so be sure to understand at what cutting speed and feed rate and cutter you will be using to cut shape, drill and countersink these. If you want the edges fancy, spend some time making them flat and true and super smooth, then heat them with a propane torch to polish them.
Laminating thin pieces is going to be frustrating and expensive and will not work well, nor be flat and true, especially over time.
I like the idea of phenolic mentioned earlier -it's super stable and dense - my Woodpecker router table is made of 1" phenolic, as are a bunch of router bases and jigs I have acquired. They stay flat and can be drilled, tapped and threaded with fine thread like metal - NOT coarse or woodscrew friendly.
Sign and display manufacturers as well as wholesale/suppliers into the plastic industry is where to shop for any of this and get proper advice. Offcuts are cheap or close to free - I always buy the guys coffee or a case of beer if they are generous and friendly - never know when you may show up there again with a question or needs.
Here are some large car audio show car systems I did in the early 90s when I was dark haired and not fat, altho far less civil. >
