What is more compatible

Question
I have a 6yr old shy, submissive male golden that is 120lbs.  We're looking into adopting another golden.  What would you suggest, male or female and why?

Answer
The conventional advice is to go with opposite sexes because they usually cooperate rather than try to dominate each other.  Of course I just answer a question where somebody's female Golden is beating up on their male.  Where you have problems is if both dogs have a strong drive for dominance.  The worst problems are with 2 dominant females.  It sounds like your male will let any new puppy dominant him as it matures.  

You might work at building up his confidence.  Start with obedience training.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  As you praise the dog for following your commands, it will build its confidence.  

Play tug of war with the dog and lose.  However at the end of the game, take the rope or toy and put it up, less the dog becomes confused about who is top dog.  Ropes from the pets' store quickly turn to hazardous shreds.   Ones I made  lasted much better.   Go to a hardware or home center that sells rope by the foot.  Buy 2' of 3/4" poly rope. Melt the ends, and tie  knots in it.   Get them as tight as possible, put it in a vise and pound it with a hammer.  Watch carefully, and be ready to discard when it comes apart.

Finally, make sure it has a den to live in.  If you are not using a crate, buy one.  The dog may be happier in its den than loose in the house.  It relaxes, it feels safe in its den.  It rests, the body slows down reducing the need for water and relieving its self.  Dogs that have been crated all along do very well.  Many of them will rest in their crates even when the door is open.  I think the plastic ones give the dog more of a safe, enclosed den feeling.  Metal ones can be put in a corner or covered with something the dog can't pull in and chew.  Select a crate just big enough for the full grown dog to stretch out in.

A dog that has not been crated since it was little, may take some work.
Start out just putting its toys and treats in the crate.  Praise it for going
in.  Feed it in the crate.  This is also an easy way to maintain order at
feeding time for more than one dog.

I am concerned about his weight.  Few Goldens should weigh 120 pounds.  You will start seeing problems long before you should if he is seriously over weight.  See http://www.longliveyourdog.com/twoplus/RateYourDog.aspx
and adjust what you are feeding if necessary.