Many years ago my coach advised me to play only power golf for six weeks because I didn't hit the ball far enough, I had good technique but no power. That was 24 years ago and for my game to date that is still the single best piece of advise I have ever received. Who cares how great your swing looks if you can't reach a long par four in two.
Just to upset people further technique is easier to learn than power.Having power although it can be lethal on a golf course is what enables you to short low scores.(power is why you can play the variety of shots needed in a single round,punch,spin,consistant draws and fades etc).
No body said you had to overswing to create power in fact you would probably loose power as theres a good chance your timing and weight distribution wont mesh together. But work on a strong release and hit thru the ball solid.
Don't swing that hard as to fall over or loose body position but you definately have to exert yourself. I can often be heard grunting on a drive. Look at the face and foreman of any photo in a golf magazine and then tell me they haven't exerted power into the shot.
Golfing muscles and weight lifting muscles are completely different, Golfers weight train but the key is train. Train there muscles for specific movements not to lift 250 pounds, check out GTO's gym/exercises