800w or 1600w strobe?

For formals in dark churches with high ceilings, is an 800w strobe not powerful enough? I want to use a large umbrella with the strobe in the center up high.

Also, if you suggest the 1600w b/c the 800w is too weak, is the 1600w too much or too powerful to also do portrait work?

I'm thinking alien bees or white lightning for the purchase.

Thanks!

You can always dial down a 1600w. Imagine if your 800w isn't powerful enough. Then again you could always try two 800s.

Let Buff be your guide!...

website says AB1600 has GN220 rating (10' f/22), so you put the light 20' away it is is f/11. With an umbrella you lose about -1EV, so you are at f/8. If you shoot at ISO 400, now you are at f/16!

website says AB800 has GN160 rating (10' f/16), so you put the light 20' away it is is f/8. With an umbrella you lose about -1EV, so you are at f/5.6. If you shoot at ISO 400, now you are at f/11!

Assess the info and make up your own mind about what you think you need.