It's totally worth it.

I've only ordered a set ring from MoissCo, so in this case I'd by the setting and stone now, then once the Amora Gem is out send it to be re-set with the new stone?

Right now the best placeholders are ashas because the cut of moissanite is different in the depth. Just make sure the Amora gem size you want to buy will work in the setting you want. The AG measurements are on the AG pages for the shape you want. Also if you are getting side stones in your ring less suggestes diamonds rather than moissanite as the color will match better if that's what you're wanting.