I like that you will get the larger cage. I had to rebuild and rebuild to keep up with my veiled. Not that I minded... but it did keep costing. I was thinking, that for 10 dollars you could get a ten gallon tank (Petco) and a few dollars in screen from ACE hardware, 1.99 per 36" X 1' and make a cage inside your cage until he or she gets bigger. The benefit of having the tank as the bottom part is that the crickets won't get away and the little git can feel like it's a real hunt, and eat hearty, whenever. Mine used to like to hang like a bat and tag them as they walked by. Just a thought. Sounds like you have been researching this a bit and want to do best for the new member of your family.
Oh yeah... and ACE has paper towel for 50 cents a roll, for the bottom of the tank so you can see and monitor fecal flow and keep all clean. Later, you can use that 10 gallon tank for breeding bugs for your cham. Good luck and enjoy the journey. :} I've been working a third job just to get my cham his equipment.