Maybe you have just been unlucky ?
The handed bit is easy to fix as taken apart they can be spun around, they should last a hecj of a while unless running near max output all the time, have you loads of stereo gear ?
A average car is fine with anything from 50Amp upwards, some have a misguided beleif that WHEEL SIZE is important, but this refers to the alternator pulley wheel, the only important bit is that at very slow speeds it won't charge as much so a smaller wheel turns it faster at the same rpm, won't give any more max power though.
You can rerwire these from STAR to DELTA phase though, this will give around 2/3 more power at lower revs, but again no more max.
tabetha