Depends on what you mean by Larger...
Going from a 55 to a more common 60, is not a change, that is less than 10% and less than 10% is "No change" when it comes to most electronics. IT is also the change I'd recommend.
70 (Well 69) is the maximum recommended (By Xantrex) recharge rate for a single pair of GC-2's in series. And I do not think anyone makes a 70... Damon put an 80 in my rig.
But for you I'd recommend a Progressive Dynamics 9260. No other change need be made. You won't need to upgrade wiring, odds are you won't even need to upgrade any fuses or circuit breakers. With a bigger unit you may have a lot more work to do.
