Have you or your stringer determined the cause of the break?
What string, gauge, and tension are you currently using?
What's your style of play? Big flat hitter? Top spin grinder?
How many hours are you getting out of each string job?
I've always had success with Luxillon polys.
With the exception of the Adrenaline line, I've tried the others in various gauges.
If you're looking for durability and willing to sacrifice some spin potential and control, the XP is a very economical string.
Tennis Warehouse is a good online site to shop strings and get reviews.
Good luck and keep us posted!
Remember, for the poly to perform at it's peak, the tension MUST BE LOWERED SIGNIFICANTLY. If you have the resources, experiment to see how low you can go!