I've got an A9 and I love it, but it's definitely a CR123 "only" light.
It's regulation is matched perfectly for CR123's and no other battery works as well.
That said, I'm perfectly happy with that because I bought it primarily as an "emergency" light for power out situations when my rechargeables won't be as useful.
I don't know how much money you have in your wallet, but I'd suggest you keep the A9 and use it with CR123's, and then get an A8 for use exclusively with 18650's as mdocod mentioned.
That way, you run free energy with your rechargeable A8 but have an excellent backup light in the A9 and your stashed CR123 "emergency" batteries.