Last year the avg matriculant cGPA was 3.72 and sGPA 3.65, so I'd hardly say that a 3.7/3.5 are considered "very low". That being said, often the research-heavy schools that I assume you're referring to have higher avg stats, but that doesn't mean your research experience won't be valuable when applying to more mid-tier schools. If you're set on going to a T20 school you may need to take more time to bring up the GPA and destroy the MCAT but otherwise I see no reason why you'd need to only target "low tiers & DO".