Trustworthy auto shops that offer affordable FULL car inspections?

I'm planning to buy a used car through a private seller, but I'm looking for a mechanics who offer affordable full pre-purchase inspections in Southwest Houston. I am fine with service that is between $150-$300, but just I want it thorough. So far, I know Christian Brothers gives pretty inexpensive pre-purchase inspections for $149.45, but I'm not sure if the inspection will be as thorough as I expect. Any suggestions for places OR how to know if they did a pretty good inspection of the used vehicle?