alternator

[Tex_h2]

Sometimes when I start the beast up it slowly cranks but will always turn over. Then my amp gauge will bounce from 11-14, no matter if I'm driving or sitting. Also, if I pull back on the window switches (window already up) the headlights and interior light will dim.

I've got a red top that is 3 years old, and also have a large amp/sub.

My question is do you'll think its the alternator or new battery??

If it is the Alternator, should I replace with stock or upgrade to a large amp?