Quarter bars means the saddle is built to fit a quarter horse, which is your "standard" Western saddle. Quarter horses are stockier and wider than a lot of other horses, so the bar spread is wider than a gaited saddle or Arab saddle (narrower horses).
If you are trying to find a saddle for your horse, it is always best to have an experienced saddler measure and fit your horse, even if you have to pay them for the time/service. It will be SO much better for you and your horse in the long run. People may tell you what they think the horse needs, but having a professional fit him can often give you a very different result. (A lot of people think that just because they throw the quarter saddle with a pad on the horse and it stays on, it therefore fits the horse just fine.)