An 80w panel normally has an Isc of about 5 amps, which is what you would expect to see with it aimed right at a high sun. 6.67 amps if that is what you are seeing at the battery, could mean you have an MPPT controller with the batts very low to get that many amps, or else your panel is more like 110w. with an 80w panel, you would normally have a simple PWM controller.
Anyway, yes you can increase the solar. But first confirm which controller you have now by brand and model, and also if you can, which panel you have. Then we can spend all your money on suggested upgrades. :)