Alternators

i run a 100 amp single wire alternator. bought a cheap chinese one that lasted not very long. then bought a tuff stuff alternator which looked identical to the last one. anyway that lasted not very long either.
both of these failed ones i had checked by my local auto electrician and his opinion was " they are rubbish units, ya get what ya pay for".
what is a good reliable brand. are the powermaster any good. peoples opinions on the please.
cheers