I have a 1998 ford explorer 5.0L. how much power can the charging system handle?

i have a 1000w amp & one sub. i run a 1 farad cap, have a Optimus battery, did the 'big 3' wiring under the hood. sounds great now. was contemplating adding a second battery, a second sub and basically doubling what i got. debating on whether i need a H/O alternator, and if so, where is a good place to get one? any tips and/or recommendations are appreciated. thanks in advance