bitmain antminer l7 9500mh z15 miner m21 56th purchase antminer s9 asic s9 se m30s+ asic miners canaan avalonminer 1066 bitmain antminer t17+ rate goldshell kd5 in inventory t19 antminer antminer t17+ 58th Whether the priority is spending budget-conscious entry-stage mining or maximizing returns