I currently have a sunn beta bass 15 combo that i run a trace elliot gp12 preamp thru. the beta has 100 watts @ 4ohms power and 300 watts total power. what would be the best way to maximize my set up? use the preamp as effect loop or use the beta as power to the pre? if anyone has any suggestions i'd welcome them. my goal is to get more power to the 15 @ 4ohms. can i use the beta as pure power?
If your cab is 4 ohms then you are at max power. You might be able to boost your input a bit but how far before the amp clips and distorts is another question.
You can't fudge the amount of power by changing how you patch in the preamp. If the amp puts out 100 watts at 4 ohms, that's what you'll get.