I've probably said this before, but I think it warrants repeating here...
Pretty much any normal (50+) hunting weight bow and arrow combination will do the job on a good broadside shot on just about any north American big game animal.
HOWEVER... bowhunting situations are difficult if not impossible to control and sometimes in spite of all our best efforts, $h*t happens... That's when more (draw weight and arrow weight) can pay dividends. It's not going to help you if you gut shoot something, or shoot something through the backstrap. However, on bone impacts, spine impacts, frontal and rear shots that sometimes occur due to (insert scenario here), the added energy will, in some cases, make the difference between recovering an animal or living with the gut aching feeling of knowing you wounded (wasted in some instances) an animal.
I am not inviting anyone to over-bow themselves or shoot a bow they can't draw back smoothly in a cold, uncomfortable position or a bow they can't shoot accurately. I'm also not promoting frontal, rear or any other shot than a broadside or quartering away shot within your effective range. But... it's my philosophy that if you can comfortably and accurately handle the extra draw weight, you might buy yourself a little safety net when $h*t happens.
I've had $h*t happen, and on a few occasions more draw weight, arrow weight, and a better broadhead choice in my estimation would have improved my odds of celebrating rather than pouting. I've since modified my equipment selections to improve my odds. In car racing, they don't dress for the race, they dress for the crash. A lot of bowhunters plan around perfect. Bowhunt long enough and eventually perfect will turn to $h... and that's when you start to really question and analyze the equipment selections you've made.
Bottom line - if you can really handle 75-80 pounds, go for it. If you can only really manage 65 comfortably, then don't try to up the draw weight or you are only going to increase the probability of a poor shot and wounding game.
Another important piece of advice... If you're going to shoot an 80 pound bow at 72 pounds, then you're better off to bottom out the bolts on a 70 pound bow and you'll get the same 72+ pounds and more performance. Bows perform better when they're bottomed out.
Clunk, clunk... (that was me stepping down off the soap box).
Good luck and shoot straight!!
Coop