Yup, that's the only problem with a single case, Once you're in low range you are stuck in super low.
Dual cases give you the option of using the same stock gear ratio that you are now and then shifting the Crawler into low when you need to be super low (doubled down).
A Dual case setup is 2.28x2.28 = 5.2:1 which is lower then just a single case with aftermarket gears.
About the A/A 5.0 gears I would HIGHLY recommend reading what I have here:
http://board.marlincrawler.com/index.php?topic=4310.msg38627#msg38627
BigMike
