500w light bar, do I need a stronger alternator
 

I have a 500w 52" light bar on the way but I'm unsure if I will need to swap out my stock alternator. Truck is a 2000 F150 4.6 V8 which I believe has a 90 amp alternator. I don't have any other extra lighting on the truck and just the stock stereo. Do I need to get a 130 amp or even higher? Electricity isn't my thing, thanks.

Most chinese 50-52" light bars are rated at 300w, so I wonder what the true output/draw of yours will be.
I have 3 x 30" 180w bars (540w total) and I don't have a problem with my 05 powering all those, the high beams, and my subwoofer. When I hit the lights, my battery voltage drops from ~14.4v to ~13.7v.

500w light bar, do I need a stronger alternator
 

You are correct, all these Asian bars state X amount of watts based of the number of leds. The true wattage isn't even close. You'll be fine with the stock alternator