Mike,
If the species scratches a lot and/or needs a flooded substrate it might change your requirements.
Every furniture-to-cage conversion is different depending upon how the unit in questions was constructed. I know there are websites out there describing this process but I don't remember where they are nor do I think they'll help much.
Regarding the epoxy, I have used pool paint epoxy, fiberglass resin, and pourable bartop epoxy.
The pool paint epoxy would work if the inside of the dresser has a lot of framing supports that need to be painted over and/or if the interior wood is not all that attractive. BTW, make sure it's not cedar due to toxicity concerns.
Pool epoxy has nasty solvents and is a pain to work with. But boy it protects well.
The bartop epoxy is great if you want a clear coat and have flat surfaces to apply it too. It has self-leveling properties so you really can't brush it up the sides of a framing member and expect it to stick.
These epoxies probably don't have great scratch resistance but they are easy to use and there is no concern with nasty solvents.
Fiberglass resin I just don't recommend, although I do understand that there is a form that is pourable like the bartop epoxy that is also super clear and sandable. I have only used the ugly automotive epoxy. Nasty stuff.
Comparing cost of these products is difficult. They are likely all priced the same on a per-gallon-basis, they the require different thickness' so you have to factor that in.
Pool paint epoxy is probably the cheapest since it can be applied so thin but you have to buy two gallons (gallon of resin and a gallon of activator).
I would only use the clear, sandable/pourable fiberglass resin. I have never priced it nor do I know how thick of a film it requires. As such, I simply have no idea how much it will cost.
Bar top epoxy, supposedly, requires a very thick build, making it the most expensive. But you can often find Envirotex in small kits, meaning you don't have to buy so darn much and store the excess.
However, I ate at Outback Steakhouse last night and noticed that my table had a very thin build of this epoxy and the table was still in great shape. I may experiment with these epoxies again and see if I can apply a thin build and still get excellent protection.
Okay, in summary:
Decide if you want a clear or tinted coat.
Decide if the design of this dresser requires the epoxy to be brushed on or if it could be poured on.
Combine your two answers and go from there, pay particular attention to the needs of the species that will go in the cage.
Sorry to ramble.