I bought many of these.
http://cgi.ebay.com/RC-Car-Brushless...item255fbd225c
http://cgi.ebay.com/RC-Car-Ezrun-13T...item5196bbbc4a
They are genuine HobbyWing. And very cheap...
And your 20C batteries should be good. My own testing show me that 35C or 20C makes no difference.