It will be hard to lose 20lbs and gain muscle at the same time. As I'm sure you already know muscle weighs more than fat. I would recommend loosing the weight first then try to build up muscle.
Hydroxicut HARDCORE or EXTREME work great for loosing weight, but you have to make sure you take it as directed, EVERY day or it won't work

I personally like the supplements that MuscleTech offer. I would check them out.

Whey Protein, I haven't takin it in awhile but I'm about to start again. I would do one whey protein shake in the morning. Then another at night, or after you work out. It's important to get protein in your body as soon as possible after working out. To help your muscles absorb the protein even better, take some sort of supplement or pills that have amino acids in them.