I have a 93 civic with a 70 amp alternator. Right now the alternator is producing too much voltage( up to 20 volts) I suspect that my 900 watts rms stereo system(mtx tc 4001 front chan. @ 4 ohms rear chan. @ 2 ohms, mtx mxa6001 A 2ohms) is to blame. So I decided to get a HO alternator, but the closest guy that does it is in brampton a few hours drive. After doing some homework I found out that added a second isolated battery may provide better protection. Does anybody have any advice, pros or cons and what would you do? HO aternator, Second battery or both? I have already upgraded my battery and wireing for those who will ask.

__________________
1993 honda civic dx
Security: compustar 2way
Head Unit: Alpine 9886
Amps: MTX mxa6001, MTX TC4004
Wiring: stinger
Mids & Tweeters: mb quartz rc216
Sub: 12" ssd fi audio in custom ported box(2.6 cu ft) tuned to 32 Hz
SPL: 140.3 at the dash at 38hz(Door open)138.7 with music tested with a term lab mic