Ahh, I think you're confusing Amps and Watts.
Actually somewhere between 75 Watts and 5 Watts is a pretty good choice for most of us. Most solar
panels are rated in Watts.
If you check the left you'll see under Tutorials, Solar. That's a good place to start. If you follow the calculations there you'll get an idea of what you'll need.
You might not even need a solar panel
if don't stay in one place for more than 3 or 4 days. Your tow vehicle should recharge the battery
between camping locations.
A 75 Amp solar panel
would be 75 Amps x 17.5 Volts = 1,312.5 Watts. or 1.3 Kilowatt.