In a medium saucepan, heat the half-and-half milk over medium heat until it just starts to boil.
Reduce the heat and add the Velveeta cheese, stirring continuously until melted.
Add in the grated cheddar cheese, stirring continuously so that the cheese melts evenly into the mixture.
Add the diced tomatoes, salsa, cream cheese, jalapenos, cumin, cayenne pepper and chili powder. Stir until all of the ingredients are blended together.
Simmer on low heat for 5 minutes or until everything is melted and combined together.
Serve immediately with tortilla chips.