My upgraded alternator was about $550 plus a bit more for the external voltage regulator...

Spyder Man is right...we sorta need to know brand, model, and how your wiring the amps to know the best route to suggest.

There is the off chance you might be ok with just upgrading the wiring in the car (BOTH power and grounds) to something like 4 gauge.

Alternator is a good idea, but might not be needed. Battery? Again, a possibly good idea, but maybe not yet. Caps? depends also....

John