Thanks for your quick reply.
So if I am able to complete undergrad with a cGPA = 3.5, sGPA=3.4, and then complete a SMP instead of a Master's in say... Microbiology, the SMP would help my application more?
Do schools screen for their 50th percentile GPA or what?
Nobody(outside of perhaps a small handful of absolute top tier schools) screens out for a 3.5 GPA.
You don't need an SMP as much as you do a) A strong MCAT score b) Good EC's and an early well written application. Your GPA is above the 10th percentile for many fine schools and within a standard deviation of MD matriculants. It's below average, but with it a good MCAT score you can work with it
The average GPA for even top SMPs is around 3.3/3.15. You are well above that. It'd probably be a less risky route to do DIY post bacc work to try and get your GPA around 3.6/3.5. If you can get your numbers near that, you should have a competitive workable GPA.
If you want to do an SMP go ahead. Yes, if you ace one, it'll help you out a lot. But SMPs are also rather risky in their nature; do you think you have what it takes to beat out 60+% of MS1's on their exams? Because that's what you'll need to do in an SMP really. And these programs are also expensive as hell and the unofficial "linkage" of these programs to their host med school is also declining. In other words, there's a lot of risk. Just to give you an idea check out this forum, in particular page 3-5.
http://forums.studentdoctor.net/threads/university-of-toledo-msbs-2015-2016-smp.1114197/
Long story short, the Toledo SMP program historically took about 65% of their grads into Toledo's SMP program. But last year the number dropped down to 20% out of nowhere? Why? Because SMP grads aren't a high priority for many med schools; they are the ones with the lowest UG stats. Hence, you can never predict how a school will treat its SMP grads and shove them to the side. They simply arent the schools priority. Note, this same exact type of thing has happened at other SMP programs such as Eastern Virginia, and Drexel.
Do your research on SMP programs. Study hard for the MCAT. Assess how realistic you think it is that you can out performance many MS1's in their classes who will have better UG GPA's than you and will now be studying way more than they did in UG. The SMP route is a good one for many, but it's also a poor choice for many; a poor choice that will have lots of repercussions.