You really need to figure out what type of fighter you are naturally. Are you a defensive guy that plays with his opponents and strategizes for a while making small incrimental attacks or are you more aggressive and find your natural comfort in destroying your opponent as soon as possible. Both have their advantages/disadvantages, but finding out which you are more predisposed to doing naturally will help determine your training.
I use to be a distance fighter(thin but fast and could go for hours), until I praticed more practical arts and realized the huge asset strength and power really were. Of course its only my opinion, but I think that the cyclic doctrine of stamina and negativity towards bulk is outdated by a new generation of fighters that realize the potential of being able to devastate opponents more quickly. Obviously boxing doesn't place the immediately quick time demands as a real fight does, but being able to demolish your opponent with awesome power has been lost in many boxing schools that stress too much cardio. Of course stamina is important. And if you're a close equal to your opponent, the potential of a loss increases with time, but again it depends on you. Anyway, find your strengths and build upon those.
For now, at your size, I would focus on size and power...continue the 5X5 and train in fighting to a low extent that minimizes cardio for a few years, so you can learn the combative strategies, gain knowledge, yet still keep muscle gains.
I hope you understand my ramblings, I'm on some vicodin and Somas
Anyway, who wants to see 2 130 lb guys dance for a dozen rounds, when the excitement and true nature of combat is found within the knowledgable and powerful heavyweights.
