upgrading 2prong power cord on CJ SA250 amp -help

I have a used Sonographe SA250 amp (low end Conrad Jophson make) - came with a non-detachable old skinny zip cord.

Should I go to 3 prong? Sounds a little tricky for me.

Or just resolder on a much fatter 2 prong cord - like the fattest one I can find at homedepot. (stranded or solid?)

Or - use a 3 prong cord - but leave the ground unconnected as a sheild? Which end would stay unconnected..?
Hit up C-J on their website for the info, they're very good at getting back and providing reasonable info to questions like this