Would this be an ideal home for an adult iguana

Better yet, give him his own room, or the run of the house like a cat or dog. You could keep him in your room (Iguana proofed of course) while you are out, then let him run around the house when you are home watching him.

I want to mention something about large cages (or free roam of the house). If you buy a baby Iguana, it is a good idea that his cage grows with him. If you stick a baby into a huge cage (or let him run loose), he can get lost. If he can't find food and heat easily he may die. If you can't find him for bonding time he may not appreciate company when he is older. If you have to chase him down everytime, you may injure him and he won't be as easily tamed.

Consider getting the larger of the cages you mention for him while he is small, then transfer him to the larger cage (or room) when he outgrows it.

Always read books in addition to reading websites. Books have the most accurate information. Talk to people who own Iguanas and reptile store owners. Not Petco or Petsmart those people are idiots.

I mentioned Iguanas get BIG. I also want to mention that a lot of them HATE dogs. If the Iguana gets to be the size of a cat, (and it will) with a 4 foot tail, it can do a dog some serious damage. I'm not exagerating sizes. They get HUGE!

Hope this helps.

Check bird cage manufacturers. They have some really cool new cages out that look great and are huge.

Look up Bearded Dragons. They would love the cage sizes you mention. Iguanas might be larger than you want.