I find it difficult to think that a lot of weight training would be beneficial to an endurance athlete. I come from almost 20 years of weight training and believe that muscle mass takes metabolic energy to sustain it, even when it (the muscle) is not in use. This would seem counter-productive to essence of aerobic exercise.
Moreover, for a 160 lb. athlete to do sets of 170 lb in the bench press seems a difficult feat. In my experience few people that use ONLY weight training as their preferred mode of exercise can do sets of bench presses with body weight!
Remember, you have over 600 muscles in your body. How many do you think you really exercise doing mostly cardiovascular activity (swim, bike, run)?
Having said that, I do believe adding weight training to your triathlon regimen will improve your overall fitness level, but may raise your times. It's difficult to do both very well, as I see them as counterproductive for seasoned athletes.