I've considered that option, but since my car is practically a daily driver i would like to keep all the trunk space that i can. To be honest I'm not a fan of most car audio caps, as to get any real performance advantage you would have to really go all in on some very expensive and bulky banks. As well as installing a second battery, just too bulky and heavy for my application. I'm actually already running a H6 AGM for my primary battery, which I may still upgrade to a XS Power in the future.
I may be a bit of a novice, but i think my battery is pretty well up to the task. Voltages are actually staying nearly identical to before when I was running 300 watts to a subwoofer vs 1400 now.
Only REAL reason i want to upgrade the alt is because of the noises it sometimes makes now. I think its just seeing a bit too much abuse ATM.