Howdy, I have posted this before but still find it valid.
Our rig came with a 9100 series PD unit, with the charge wizard, which is the back up for the new unit.
I went to a Xantrex inverter / charger with a 100A charge rate.
We dry camp, mostly, and find the dual purpose unit really handy.
Our rig has 4 T-105'a for a 450AH bank with a 12v 175AH backup slaved to a 4 position selector / disconnect.
The common belief is that the charge rate should be aprox 10% of the AH reserve, mostly as a safety concern.
I called Trojan before setting up my system and the tech told me that a 25% charge rate was optimum, for what it is worth.
If we used primarily used hook-ups I would not have changed anything.
Here is a link to the unit I purchased, refurbished, for about 1/2 the MSRP.
One other note, the installation, with controls, will cost as much as the unit.
http://www.xantrex.com/web/id/49/p/155/pt/9/product.asp