how big of a cap?

[Spades]

I have been running a 1 farad and never noticed headlights dimming with my old set up...was running my components off deck power and the subs were using a sony 1200w amp. i doubt it could hit 1200w unless lightning struck it, hance why my headlights never had dimming issues i suppose. but, i am adding a 300w jensen amp into the mix now, and the deck will be upgraded, so the power draw will be increasing.

so, think i am fine keeping the 1 farad or should i look at getting a extra cap as well?

edit: added 300w amp brand name