I agree with both Matt and BK regarding bodybuilders. There are a few natural ones out there who are pretty fit, but these are the exceptions. For the most part, bodybuilders tend to lack "pound for pound" strength. That is to say, the functional strength of most bodybuilders is relatively low compared to their puffed-up size.
On the other hand, I do believe a person can get big and strong, yet remain extremely fit. Yes, it takes more energy to move a large body than it does to move a small one. However, if the body is the right kind of big (that is, consisting of functional, quality muscle, and powered by a well-conditioned heart and lungs), it will generate the energy needed to get the job done.
I'm a big advocate of "pound for pound" strength. If you're going to add muscle to your frame, make sure it'll help you function better. Of course, there is usually a limit to how big a person can get before the added size begins to reduce functionality, and this is determined by a number of factors, mostly genetic (height, skeletal frame type, muscle connections/ insertion points, etc.). Big Khanz is a huge guy, with considerable height and a large skeletal frame. He is able to carry a tremendous amount of muscle while remaining extremely functional and athletic. A fine-boned man who stands 5-feet tall wouldn't be able to remain very functional if he carried the same amount of muscle. I'm somewhere "in the middle," standing 6-feet tall at about 230 pounds... not huge, but not a small man, either. My goal weight is actually a solid 200-210, so I've got a bit of unneeded adipose to dispose of. Still, I'm quite athletic, and I've dragged many a large animal out of the woods!
My advice, in a nutshell, is this: Don't get big just for the sake of getting big, but don't be afraid of packing on quality muscle, either. Just make sure you're strengthening your body on the inside, too (heart, lungs, connective tissues, etc.). Form follows function. Don't worry, if you work hard to make yourself stronger, you'll look the part.
Tantalar, being that you and I are about the same height, I thought you might be interested in this picture of me, taken at a bodyweight of about 215 pounds. As you can see, there's a fair amount of muscle there, but every bit of it is functional.
