Ply wood is about the safest you can use.. Because it is made out of layers of veneer glued with the wood grain in crosspattern. And because any wood always reacts and works due to inveronmental conditions, temperature, air humidity and the humidity in the wood itself it can bend over time. If it does it will always bend from the middle towards the centre, inworths or outwords depending which side you put on top.
Like this
The plywood layers and the grain cross pattern prevents this, because every layer counteracts to the next.
This doesn't mean that using any type of other wood is out of the questions.. Once wood is fully dried and stored in a relative constand inveronment it stays rather as is. I builded my stand from 1¼" steel pipe topped with 4 cm thick fully cured douglaspine (very popular pine wood for furniture build) beams, 5 pieces screwed together, each next one oppisite grain direction from the other and machine flattened afterwords and sealed with varnish. Once fully cured (well dried) and sealed, with this thickness it is unlikely ever to bend again.
So it's a bit of a trust issue you have with the supplier of the furniture wood, if he says it fully curred you have to take for granted it is.. And probably in risk to have to do some mopping afterwards if it wasn't.
Anyway plywood is the saffest and easiest to use, almost all regular furniture is plywood decorated with veneer toplayer. But any good quality hardwood doesn't need to be an issue. You could reinforce an already excisting cabinet.
Any other material than wood based, you should make sure it doesn't react to much to inveronmental conditions like temperature. But i can't realy think of anything cost effective and easy to handle material as alternative for a diy project.. But a lot is possible, i have an aquarium standing on a cabinet with marble top plate. It's literaly rock solid..
And an aqaurium standing on a completely Cherry wood table.
Dimesnions and weight ofcourse also play a major role in how high the risk of failure is..