Without seeing you fly, it's really not possible to say if you could handle a warbird or not. But odds are against it. Most warbirds (the AT-6 included) have some pretty nasty stall charastics, making them a lot harder to land than a trainer like the Avistar. I've seen plenty of guys get ahead of themselves and plant a warbird just because they got a little too slow or turned a little too tight in the landing pattern. Half the time, they walk around saying "I was hit, who's on my frequency, how did that happen?" while the rest of us are muttering "classic accelerated stall".

If you think you are ready to move beyond the avistar, get one of the planes mentioned in the "second plane" threads on here. There are lots of options with lots of different appearances.

If you do get the warbird, get it up high quickly and then get to work on feeling it out at low speeds. Best to do your first snaproll when you have altitude to get out of it. Just remember to let the speed build back up after the stall. Warbirds take a while to get back to speed after a stall, you can't just hold the up elevator and count on it pulling out eventually like you can with a trainer. "a little up makes you go up. A lot of up makes you go DOWN".