any cube. by the time he works his way down to 1:20 (if he doesnt lube a storebought) from 6 minutes, he will have a nice broken in storebought by the time he is at 1:20.. with lubing and a method other than beginners, he would easily be able to break 30 sec with a nice broken in, lubed storebought. if he is looking for a decent speedcube, just go with one of the popular ones like dayan lingyun v2, zhanchi, guhong or even some of the nice older 'classics' like an a5 or something