The funny thing is that those BSL6's do not have as much piston area as your stock calipers do.
You have six varibles to play with: Rotor diameter, Caliper Piston Area, Caliper Rigidity, Pad Compound, Pad Thickness, and Rotor Width.
Of those, the greatest rewards will be found in increasing the Rotor Diameter. More braking torque, think of this as going to a longer stroke crankshaft. As a general rule your maximum rotor diameter will be 2" smaller than your wheel size. Contour of the wheel around the outer edge of the rotor and the caliper selected play a role in this.
Changing the Caliper Piston Area opens up a potential can of worms if you stray too far from the piston area you have now. This is the cause of at least 90% of disc brake swap complaints.
The GM calipers are not especially rigid (no sliding caliper I've seen is) so do NOT buy those made from aluminum unless you're putting them on the front of a roundy car. BSL6's are pretty stiff.
The point of second greatest rewards is in Pad Compound. Suggest that you try some wilwood "D", "E", or "J" compound pads b4 you do anything else.
Pad Thickness is a wear life item only. Thicker pads last longer. Cup cars at Martinsville finish on metal to metal when they started with 1.1" thick pads.
Rotor Width is a heat rejection determiner. The wider the vents btwn the friction surfaces the more heat the rotors can dump into the atmosphere. In the dirt it's hard to get much pad temp anyway so wider rotors won't gain you much.