I have no experience with two speed pumps but I know Pentair, Hayward, and Jandy all make quality pumps. For a few $$ more you could get yourself a variable speed pump. Check with your utility company, they may offer a rebate on dual and variable speed pumps. Swimming Pool Pumps - Inground Pumps - INYOPools.com
Keep in mind the pump assembly is two pieces; pump & motor. You could upgrade to a two speed motor if your pump is still good. Tolber Electric Motor in Garland has the motors and will change it out for you if you bring the entire pump assembly in.