The Hobbywing 60amp ESC will be more then enough to run a 540 motor in the MERV and has a pretty small footprint .
As for rockers , stay with the stock ones and get some aluminum push rods and toe links and steel hollowballs . RPM a arms are a must but I would get GPM aluminum hubs and not RPM as they will get sloppy quickly like the stockers do . You can also get the revised pillow ball inserts from traxxas that screw into the stock hubs to take out the slop .
The GPM shocks are OK but the springs are pretty stiff , but thet are better than stock IMO .