I almost bought one of those when they first came out but they only run on primary's and RCR is not recommended. This thing would cost a fortune to operate and fill the landfills in the process. Some interesting reading:
I have the T25 R5 and highly recommend it. It runs on 2 x AA's (I use Eneloops) and its a powerhouse. Great if you don't want to run expensive primary's or 16340's of the T20.
No but it is driven hard on Eneloops and doesn't get hot. You can keep it in turbo for the entire burn. The driver is well optimized for 3.0V and automatically steps down to medium mode as the batteries become depleted.
Check out CPF for more answers but the A6 seemed terribly underdriven when compared to the Fenix TK40 (both multi AA lights). For the price, Id look into other options if you wanted a budget MC-E light. TK40's sometimes sell at ridiculously low prices too. There's also the TK30 (2 x 18650) but with the same head design.
Im going to wait for others to get their XM-L mods up and running and see who has the best combination before I do anything. Everything with the XM-L is still speculation with no results.