DO NOT buy a bike that's too small, no matter what anybody tells you about "making it work" with a new seatpost, stem, whatever. I'm 6'4" and feel very cramped on anything smaller than 64cm, but YMMV.
Don't get fixated on carbon or aluminum, especially in a low-priced bike. Each frame material has advantages and drawbacks, and many of us prefer steel.
Your weight isn't likely to be a problem as long as you buy decent wheels, but your height will be. This is a sport where a 5'11" guy is a giant.