Why not just straight aluminum?
I’m much more familiar with enameled cast iron for cooking, not brewing. It will chip if dinged, but not a biggy when on aluminum for brewing. But, why add extra weight to your boil pot with the enamel?
If you go the aluminum boil pot route I’d suggest get the thickest gauge you can afford to avoid scorching and don’t use pbw or oxyclean on it if you do scorch it.
Something I have learned with many hobbies and interests. If you really are planning on doing your hobby for any length of time bite the bullet up front and spend a little extra to get the good stuff (in this case; thicker bottom, heavier gauge, larger size) because if you don’t you can find yourself re-buying it again.
I didn’t answer your question but rather gave my sideways opinion. 
All-grain is fun, enjoy! Good Luck :cheers:
Brew On