I'm 20, 6'5, 228pounds with around 22-23%BF

I feel like I've done enough cardio, not that I'm going stop just reduce it a little bit(or not because I need to lose more BF). I usually run 3 miles on the treadmill Mon-Fri and lost 45 pounds so far. I'm not sure what supplement to buy, friend of mine suggested Optimum Whey but I wanted to take advices from experienced lifters like you guys. My next goal is to drop down to 15%BF so I don't want something thats heavy.

I'm going to start Ronnie's STS workout cycle this coming week. I feel like my body got used to the treadmill, would the elliptical show me better results for cardio?

Please feel free to criticize, Thanks in advance.